Category Archives: Shooting Tips

cinematography, Shooting Tips

Why do we strive to mimic film? What is the film look anyway?

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Please don’t take this post the wrong way. I DO understand why some people like to try and emulate film. I understand that film has a “look”. I also understand that for many people that look is the holy grail of film production. I’m simply looking at why we do this and am throwing the big question out there which is “is it the right thing to do”? I welcome your comments on this subject as it’s an interesting one worthy of discussion.

In recent years with the explosion of large sensor cameras with great dynamic range it has become a very common practice to take the images these cameras capture and apply a grade or LUT that mimics the look of many of todays major movies. This is often simply referred to as the “film look”.

This look seems to be becoming more and more extreme as creators attempt to make their film more film like than the one before, leading to a situation where the look becomes very distinct as opposed to just a trait of the capture medium. A common technique is the “teal and orange” look where the overall image is tinted teal and then skin tones and other similar tones are made slightly orange. This is done to create colour contrast between the faces of the cast and the background as teal and orange are on opposite sites of the colour wheel.

Another variation of the “film look” is the flat look. I don’t really know where this look came from as it’s not really very film like at all. It probably comes from shooting with a log gamma curve, which results in a flat, washed out looking image when viewed on a conventional monitor. Then because this look is “cool” because shooting on log is “cool” much of the flatness is left in the image in the grade because it looks different to regular TV ( or it may simply be that it’s easier to create a flat look than a good looking high contrast look). Later in the article I have a nice comparison of these two types of “film look”.

Not Like TV!

Not looking like TV or Video may be one of the biggest drivers for the “film look”. We watch TV day in, day out. Well produced TV will have accurate colours, natural contrast (over a limited range at least) and if the TV is set up correctly should be pretty true to life. Of course there are exceptions to this like many daytime TV or game shows where the saturation and brightness is cranked up to make the programmes vibrant and vivid.  But the aim of most TV shows is to look true to life. Perhaps this is one of the drivers to make films look different, so that they are not true to life, more like a slightly abstract painting or other work of art. Colour and contrast can help setup different moods, dull and grey for sadness, bright and colourful for happy scenes etc, but this should be separate from the overall look applied to a film.

Another aspect of the TV look comes from the fact that most TV viewing takes place in a normal room where light levels are not controlled. As a result bright pictures are normally needed, especially for daytime TV shows.

But What Does Film Look Like?

But what does film look like? As some of you will know I travel a lot and spend a lot of time on airplanes. I like to watch a film or 2 on longer flights and recently I’ve been watching some older films that were shot on film and probably didn’t have any of the grading or other extensive manipulation processes that most modern movies go through.

Lets look at a few frames from some of those movies, shot on film and see what they look like.

Lawrence of Arabia.

The all time classic Lawrence of Arabia. This film is surprisingly colourful. Red, blues, yellows are all well saturated. The film is high contrast. That is, it has very dark blacks, not crushed, but deep and full of subtle textures. Skin tones  are around 55 IRE and perhaps very slightly skewed towards brown/red, but then the cast are all rather sun tanned. But I wouldn’t call the skin tones orange. Diffuse whites typically around 80 IRE and they are white, not tinted or coloured.

Braveheart.

When I watched Braveheart, one of the things that stood out to me was how green the foliage and grass was. The strong greens really stood out in this movie compared to more modern films. Overall it’s quite dark, skin tones are often around 45 IRE and rarely more than 55 IRE, very slightly warm/brown looking, but not orange. Again it’s well saturated and high contrast with deep blacks. Overall most scenes have a quite low peak and average brightness level. It’s quite hard to watch this film in a bright room on a conventional TV, but it looks fantastic in a darkened room.

Raiders Of The Lost Ark

Raiders of the Lost Ark does show some of the attributes often used for the modern film look. Skin tones are warm and have a slight orange tint and overall the movie is very warm looking. A lot of the sets use warm colours with browns and reds being prominent. Colours are well saturated. Again we have high contrast with deep blacks and those much lower than TV skin tones, typically 50-55IRE in Raiders. Look at the foliage and plants though, they are close to what you might call TV greens, ie realistic shades of green.

A key thing I noticed in all of these (and other) older movies is that overall the images are darker than we would use for daytime TV. Skin tones in movies seem to sit around 55IRE. Compare that to the typical use of 70% zebras for faces on TV. Also whites are generally lower, often diffuse white sitting at around 75-80%. One important consideration is that films are designed to be shown in dark cinema theatres where  white at 75% looks pretty bright. Compare that to watching TV in a bright living room where to make white look bright you need it as bright as you can get. Having diffuse whites that bit lower in the display range leaves a little more room to separate highlights from whites giving the impression of a greater dynamic range. It also brings the mid range down a bit so the shadows also look darker without having to crush them.

Side Note: When using Sony’s Hypergammas and Cingeammas they are supposed to be exposed so that white is around 70-75% with skin tones around 55-60%. If used like this with a sutable colour matrix such as “cinema” they can look quite film like.

If we look at some recent movies the look can be very different.

The Revenant

The Revenant is a gritty film and it has a gritty look. But compare it to Braveheart and it’s very different. We have the same much lower skin tone and diffuse white levels, but where has the green gone? and the sky is very pale.  The sky and trees are all tinted slightly towards teal and de-saturated. Overall there is only a very small colour range in the movie. Nothing like the 70mm film of Laurence of Arabia or the 35mm film of Braveheart.

Dead Men Tell No Tales.

In the latest instalment of the Pirates of the Caribbean franchise the images are very “brown”. Notice how even the whites of the ladies dresses or soldiers uniforms are slightly brown. The sky is slightly grey (I’m sure the sky was much bluer than this). The palm tree fronds look browner than green and Jack Sparrow looks like he’s been using too much fake tan as his face is border line orange (and almost always also quite dark).

Wonder Woman.

Wonder woman is another very brown movie. In this frame we can see that the sky is quite brown. Meanwhile the grass is pushed towards teal and de-saturated, it certainly isn’t the colour of real grass.  Overall colours are subdued with the exception of skin tones.

These are fairly typical of most modern movies. Colours generally quite subdued, especially greens and blues. The sky is rarely a vibrant blue, grass is rarely a grassy green. Skin tones tend to be very slightly orange and around 50-60IRE. Blacks are almost always deep and the images contrasty. Whites are rarely actually white, they tend to be tinted either slightly brown or slightly teal. Steel blues and warm browns are favoured hues. These are very different looking images to the movies shot on film that didn’t go through extensive post production manipulation.

So the film look, isn’t really about making it look like it was shot on film, it’s a stylised look that has become stronger and stronger in recent years with most movies having elements of this look. So in creating the “film look” we are not really mimicking film, but copying a now almost standard colour grading recipe that has some film style traits.

BUT IS IT A GOOD THING?

In most cases these are not unpleasant looks and for some productions the look can add to the film, although sometimes it can be taken to noticeable and objectionable extremes. However we do now have cameras that can capture huge colour ranges. We also have the display technologies to show these enormous colour ranges. Yet we often choose to deliberately limit what we use and very often distort the colours in our quest for the “film look”.

HDR TV’s with Rec2020 colour can show both a greater dynamic range and a greater colour range than we have ever seen before. Yet we are not making use of this range, in particular the colour range except in some special cases like some TV commercials as well as high end wild life films such as Planet Earth II.

This TV commercial for TUI has some wonderful vibrant colours that are not restricted to just browns and teal yet it looks very film like. It does have an overall warm tint, but the other colours are allowed to punch through. It feels like the big budget production that it clearly was without having to resort to  the modern defacto  restrictive film look colour palette. Why can’t feature films look like this? Why do they need to be dull with a limited colour range? Why do we strive to deliberately restrict our colour pallet in the name of fashion?

What’s even more interesting is what was done for the behind the scenes film for the TUI advert…..

The producers of the BTS film decided to go with an extremely flat, washed out look, another form of modern “film look” that really couldn’t be further from film. When an typical viewer watches this do they get it in the same way as we that work in the industry do?  Do they understand the significance of the washed out, flat, low contrast pictures or do they just see weird looking milky pictures that lack colour with odd skin tones? The BTS film just looks wrong to me. It looks like it was shot with log and not graded.  Personally, I don’t think it looks cool or stylish, it just looks wrong and cheap compared to the lush imagery in the actual advert (perhaps that was the intention).

I often see people looking for a film look LUT. Often they want to mimic a particular film. That’s fine, it’s up to them. But if everyone starts to home in on one particular look or style then the films we watch will all look the same. That’s not what I want. I want lush rich colours where appropriate. Then I might want to see a subdued look in a period piece or a vivid look for a 70’s film. Within the same movie colour can be used to differentiate between different parts of the story. Take Woody Allen’s Cafe Society, shot by Vittorio Storaro for example. The New York scenes are grey and moody while the scenes in LA that portray a fresh start are vibrant and vivid. This is I believe important, to use colour and contrast to help tell the story.

Our modern cameras give us an amazing palette to work with. We have the tools such as DaVinci Resolve to manipulate those colours with relative ease. I believe we should be more adventurous with our use of colour. Reducing exposure levels a little compared to the nominal TV and video – skin tones at 70% – diffuse whites at 85-90%, helps replicate the film look and also leaves a bit more space in the highlight range to separate highlights from whites which really helps give the impression of a more contrasty image. Blacks should be black, not washed out and they shouldn’t be crushed either.

Above all else learn to create different styles. Don’t be afraid of using colour to tell your story and remember that real film isn’t just brown and teal, it’s actually quite colourful. Great artists tend to stand out when their works are different, not when they are the same as everyone else.

 

cameras, lenses, Shooting Tips, Travel

The Dangers Of Hidden Moisture.

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Electronics and water are two things that just don’t match. We all know this and we all know that dropping a camera into a river or the sea probably isn’t going to do it a great deal of good. But one of the very real risks with any piece of electronics is hidden moisture, moisture you can’t see.

Most modern high definition or 4K pro video cameras have fans and cooling systems designed to keep them operating for long periods. But these cooling systems mean that the camera will be drawing in air from the outside world into the cameras interior. Normally this is perfectly fine, but if you are operating in rain or a very wet environment such as high humidity, spray, mist, fog etc it will mean a lot of moisture circulating through the camera and this can be a cause of problems.

If the camera is warm relative to the ambient temperature then generally humid air will simply pass through the camera (or other electronics) without issue. But if the camera is colder than the airs dewpoint then some of the moisture in the air will condense on the cameras parts and turn into water droplets.

A typical dangerous scenario is having the camera in a nice cool air conditioned car or building and then taking the camera out of the car/building to shoot on a warm day.  As the warm air hits the slightly colder camera parts moisture will form, both on the outside and the inside of the cameras body.

Moisture on the outside of the camera is normally obvious. It also tends to dry off quite quickly, but moisture inside the camera can’t be seen, you have no way of knowing whether it’s there or not. If you only use the camera for a short period the moisture won’t dry out and once the fans shut down the cameras interior is no longer ventilated and the moisture stays trapped inside.

Another damaging scenario is a camera that’s been splashed with water, maybe you got caught in an unexpected rain shower. Water will find it’s way into the smallest of holes and gaps through capillary action. A teeny, tiny droplet of water inside the camera will stay there once it gets inside. Get the camera wet a couple of times and that moisture can start to build up and it really doesn’t take a lot to do some serious damage. Many of the components in modern cameras are the size of pin heads. Rain water, sea water etc contain chemicals that can react with the materials used in a cameras construction, especially if electricity is passing through the components or the water and before you know it the camera stops working due to corrosion from water ingress.

Storing you delicate electronics inside a nice waterproof flight case such as a Pelicase (or any other similar brand) might seem like a good idea as these cases are waterproof. But a case that won’t let water in also won’t let water and moisture out. Put a camera that is damp inside a wateproof case and it will stay damp. It will never dry out.  All that moisture is gong to slowly start eating away at the metals used in a lightweight camera body and some of the delicate electronic components. Over time this gets worse and worse until eventually the camera stops working.

So What Should You Do?

Try to avoid getting the camera wet. Always use a rain cover if you are using a camera in the rain, near the sea or in misty, foggy weather. Just because you can’t see water flowing off your camera it doesn’t mean it’s safe. Try to avoid taking a cold camera from inside an air conditioned office or car into a warmer environment. If you need to do this a lot consider putting the camera in a waterproof bag ( a bin bag will do) before taking the camera into the warmer environment. Then allow the camera to warm up in the bag before you start to use it. If driving around in a car from location to location consider using less air conditioning so the car isn’t so cold inside.

Don’t store or put away a damp camera. Always, always throughly dry out any camera before putting it away. Consider warming it up and drying it with a hairdryer on a gentle/low heat setting (never let the camera get too hot to handle). Blow warm dry air gently into any vents to ensure the warm air circulates inside to remove any internal moisture. Leave the camera overnight in a warm, dry place with any flaps or covers open to allow it to dry out throughly.

If you know you camera is wet then turn it off. Remove the battery and leave it to dry out in a warm place for 24 hours. If it got really wet consider taking it to a dealer or engineer to have it opened up to make sure it’s dry inside before adding any power.

If you store your kit in waterproof cases, leave the lids open to allow air to circulate and prevent moisture building up inside the cases. Use Silica Gel sachets inside the cases to absorb any unwanted moisture.

If you live or work in a warm humid part of the world it’s tough. When I go storm chasing going from inside the car to outside in the warm to shoot is not healthy for the camera. So at the end of each day take extra care to make sure the camera is dry. Not just any obvious moisture on the outside but dry on the inside. So this normally means warming it up a little (not hot, just warm). Again a hair drier is useful or leave the camera powered up for a couple of hours in an air conditioned room (good quality aircon should mean the air in the room is dry). I keep silica gel sachets in my camera bags to help absorb any surplus moisture. Silica gel sachets should be baked in an oven periodically to dry them out and refresh them.

Fogged Up Lens?

Another symptom of unwanted moisture is a fogged up lens. If the lens is fogged up then there will almost certainly be moisture elsewhere. In the case of a fogged up lens one thing that sometimes helps (other than a hairdryer) is to zoom in and out a lot if it’s a zoom or change the focus a lot. Moving the lens elements backwards and forwards inside the lens helps to circulate air inside the lens and can speed up the time it takes to dry out.

cinematography, Shooting Tips, shoots, Technology

What does ISO mean with todays cameras?

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What is EXPOSURE?

Before diving into ISO, I think it’s first important to understand what exposure is. Exposure is the amount of light you put on to a sensor or film stock. Exposure is NOT brightness, brightness is – brightness. I can take an image in to post production and make it brighter or darker, but this doesn’t change how the image was exposed. Exposure is very specifically – how much light is allowed to hit the sensor or film stock and this is usually controlled by the shutter speed, aperture as well as perhaps ND filters.

What is ISO?

Once upon a time the meaning of ISO was quite clear. It was a standardised sensitivity rating for the film stock you were using. If you wanted more sensitivity, you used film with a higher ISO rating. But today the meaning of ISO is less clear. And lets not forget, we can’t swap our sensors out for more or less sensitive ones. So what does ISO mean given that we can’t actually change the sensor?

ISO is short for International Standards Organisation. And they specify many, many different standards for many different things. For example ISO 3166 is for telephone country codes, ISO 50001 is for energy management.

But in our world of film and TV there are two main ISO standards that we have blended into one and we just call it “ISO”.

ISO 5800:2001 is the system used to determine the sensitivity of color negative film found by plotting the density of the film against exposure to light.

ISO 12232:2006 specifies the method for assigning and reporting ISO speed ratings, ISO speed latitude ratings, standard output sensitivity values, and recommended exposure index values, for electronic cameras.

Note a key difference:

ISO 5800 is the measurement of the actual sensitivity to light of film.

ISO 12232 is a standardised way to report the speed rating, ie: it is not actually a direct sensitivity measurement.

So, from the above we can deduce that with film ISO is an actual sensitivity measurement. With an electronic camera it is a speed rating, not a measurement of the sensitivity, a rating.

Different Approaches and REI.

Within the digital camera ISO rating system there are 5 different standards that a camera manufacturer can use when obtaining the ISO rating of a camera. The most commonly used method is the Recommended Exposure Index (REI) method, which allows the manufacturer to specify a camera model’s base ISO arbitrarily, based on what the manufacturer believes produces a satisfactory image. So it’s not actually a measure of the cameras sensitivity, but a rating that if entered into a standard external light meter and the shutter and aperture values from the light meter used to set the exposure will result in satisfactory looking image.
This is very different to a sensitivity measurement and variations in opinion as to what is “a satisfactory image” will vary from person to person, manufacturer to manufacturer. For example – how much noise is considered acceptable? I know a lot of people with very different opinions on this! So, there is a lot of scope for movement as to how an electronic camera might be rated and we see this in the real world where two cameras both rated at the same ISO may have very different noise levels when exposed “correctly”.

You Can’t Change the Silicon!

As you cannot change the sensor in a digital camera, you cannot change the cameras efficiency at converting light into electrons which is largely determined by the materials used and the physical construction of the sensor. So, you cannot change the actual sensitivity of the camera to light. But we have all seen how the ISO number of most digital cameras can normally be increased (and sometimes lowered) from the base ISO number.

Higher and Lower ISO values.

Raising and lowering the ISO rating in an electronic camera is normally done by adjusting the amplification of the signal coming from the sensor, typically referred to as “gain” in the camera. It’s not actually a physical change in the cameras sensitivity to light. It is more like turning up the volume on an analog radio to make the music louder. Dual ISO cameras that claim not to add gain when switching between ISO’s typically do this by an adjustment at the sensors pixel level and this is closer to an actual sensitivity change. But generally this only gives two levels, not the multitude of ISO values offed by most cameras. While it is true that Dual ISO is different to a gain shift, it does typically alter the noise levels with the higher base ISO being slightly more noisy than the lower. With a true dual ISO sensor does do is produce the same dynamic range at both ISO’s.

Noise and Signal To Noise Ratio.

Most of the noise in the pictures we shoot comes from the sensor and sensor readout circuits and this noise level coming from the sensor is largely unchanged no matter what you do.

So, the biggest influence on the signal to noise ratio or SNR is the amount of light you put on the sensor because more light = more signal. The noise remains but with more light the signal is bigger so you get a better signal to noise ratio, up to the point where the sensor clips at which point adding more light makes no further difference.

But what about low light?

To obtain a brighter image when there the light levels are low and the picture coming from the sensor looks dark the signal coming from the sensor can be boosted or amplified (gain is added) by increasing the cameras ISO value. This extra signal amplification makes both the desirable signal bigger but at the same time as the noise cannot be separated form the image the noise also gets bigger by the same amount. If we make the desirable picture 2 times brighter we also make the noise 2 x bigger/brighter. As a result the picture will be brighter but the noise will appear greater than an exposure where we had enough light to get the brightness we want and didn’t need to add gain or raise the ISO.

More gain = less dynamic range.

The signal to noise ratio deteriorates because the added amplification means the recording will clip more readily. Something that was right at the recordings clip point without adding gain may will end up above the clip point by adding gain. As a result the highlight range you can record reduces while at the same time the noise gets bigger. But the optimum exposure is now achieved with less light so the equivalent ISO number is increased. If you were using a light meter you would increase the ISO setting on the light meter to get the correct exposure.

But the camera isn’t getting more sensitive, it’s just that the optimum amount of light for the “best” or “correct” exposure is reduced due to the added amplification.

So, with an electronic camera, ISO is a rating that will give you the correct recording brightness for the amount of light and the amount of gain that you have. This is different to sensitivity. Obviously the two are related, but they are not quite the same thing.

ISO in an electronic camera is not a sensitivity value, it is an exposure rating.

Getting rid of noise:

To combat the inevitable increase in the visibility of noise and the degraded signal to noise ratio that comes from adding gain/amplification, most modern cameras use electronic noise reduction which is applied more and more aggressively as you increase the gain. At low levels this goes largely un-noticed. But as you start to add more gain there will often be more noise reduction and this will start to degrade the image. It may become softer, it may become smeary. You may start to see banding, ghosting or other artefacts. Higher noise levels are also problematic for modern high compression codecs, so even if the camera doesn’t add extra noise reduction at high gain levels it is likely that the codec will do more noise reduction in an attempt to keep the recording bit rate under control.

Often as you increase the gain you may only see a very small increase in noise as the noise reduction does a very good job of hiding the noise. But for every bit of noise thats reduced there will be another artefact replacing it.

Technically the signal to noise ratio can be improved by the use of noise reduction, but this typically comes at a price and NR can be very problematic if you later want to grade or adjust the footage as often you won’t see the artefacts until after the corrections or adjustments have been made. So be very careful when adding gain. It’s never good to have extra gain.

So what does all of this mean?

The majority of the video cameras we use today are something known as ISO invariant. This mean that the actual sensitivity of the camera doesn’t actually change, even though the camera may offer you a wide range of ISO values. Instead we are adding gain to get a brighter picture, but extra gain degrades the signal to noise ratio and limits the dynamic range.

As well as adding gain in camera we can also add gain in post production. And if the quality of the recording codec is high enough there is almost no difference between adding the gain in post production compared to adding the gain in camera. If you don’t add gain in the camera then you don’t reduce the cameras dynamic range. By moving the gain addition to post production you can retain the cameras full dynamic range and overall the end result won’t be significantly different. This is why most Log cameras use some sort of Exposure Index system that locks the camera to it’s base sensitivity as this is where the camera will exhibit the greatest useable dynamic range.

What about using Picture Profiles of different Gamma Curves?

Different gamma curves have different gain levels. So, very often you will see a camera at it’s base sensitivity (ie: no added gain) give you different ISO values depending on the gamma curve you have chosen. Again – this doesn’t meant the sensitivity of the camera is different for each gamma curve. What it actually means is that the optimum exposure (exposure = amount of light you put on the sensor) is a bit different for each gamma curve.  For example when shooting S-Log3 the sensor is exposed lower than it is with normal gammas. This darker S-Log3 exposure leaves more room for an extended highlight range. The flip side to this is that when the camera is set at the correct, no extra gain added base ISO’s “correctly” exposed S-Log3 will be noisier than correctly exposed Rec-709 or S-Cinetone, but the S-Log3 will have a greater highlight range. If you were to expose the S-Log3 and the S-Cinetone using the same aperture and shutter speed the noise would be the same.

Picture Profiles for Low Light.

A question that gets asked a lot is: What’s the best picture profile or gamma for low light?

Well,  if you have followed all of the above then you will hopefully understand that the gamma or picture profile makes no difference to the actual sensitivity of the camera.  So in reality there is very little difference between any profile or gamma curve in terms of how the camera will perform in low light. Remember: it’s always the same sensor with the same noise and same sensitivity to light no matter what other settings you have chosen.

There might be some differences in the amount of noise reduction applied in different profiles and that might make a small difference. Many of Sony cameras allow you to adjust this between off/low/mid/high. But even if you can’t change this in camera, adding a bit of extra NR in post is a common practice these days.  Really, it’s a case of choosing the profile or gamma that gives you the image you want, S-Log3 if you intend to grade, perhaps S-Cinetone if you don’t. If you bring the S-Cinetone ISO value up to match the S-Log3 ISO value, the noise in the final image from both will be more or less the same.

Using what data you have.

Perhaps the only small consideration is that under exposed S-Log3 only uses a very small part of the cameras full recording range. You won’t be making use of the full recording data range. Because of this it might be hard to grade it without the image starting to look coarse or grainy.  Because of the smaller dynamic range, similarly exposed (same aperture, same shutter speed) S-Cinetone or Rec-709 will use more of the data range and might not look quite as coarse as a result. This difference is very small, but it should be considered if you are trying to squeeze something out of an extremely under exposed situation.

cinematography, HDR, lenses, Shooting Tips, shoots

The making of “Fire and Iron”.

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I’ve been shooting with the Fujinon MK18-55mm lens on my PXW-FS7 and PXW-FS5 since the lens was launched. I absolutely love this lens, but one thing has frustrated me: I really wanted to be able to use it on my PMW-F5 to take advantage of the 16 bit raw. Finally my dreams have come true as both Duclos and MTF have started making alternate rear mounts for both the MK18-55mm and the MK50-135mm.

Fujinon MK18-55mm on my PMW-F5 using Duclos FZ mount adapter.

So, when Fujinon contacted me and asked if I would be interested in shooting a short film with these lenses on my F5 I jumped at the chance. The only catch was that this was just over a week ago and the video was wanted for IBC which means it needed to be ready yesterday. And of course it goes without saying that it has to look good – no pressure then!

First challenge – come up with something to shoot. Something that would show off the key features of these beautiful lenses – image quality, weight, macro etc. I toyed with hiring a model and travelling to the Irish or Welsh coast and filming along the cliffs and mountains. But it’s the summer holidays so there was a risk of not being able to get an isolated location all to ourselves, plus you never know what the weather is going to do. In addition there was no story, no beginning, middle or end and I really wanted to tell some kind of story rather than just a montage of pretty pictures.

So my next thought was to shoot an artist creating something. I spent a weekend googling various types of artistry until I settled on a blacksmith. The video was going to be shown in both SDR and HDR and fire always looks good in HDR. So after dozens of emails and telephone calls I found an amazing looking metalwork gallery and blacksmith that was willing for a reasonable fee to have me and another cameraman take over their workshop for a day (BIG thank you to Adam and Lucy at Fire and Iron check out their amazing works of art).

A blacksmiths forge and art gallery were chosen for the shoot.

Normally I’d carry out a recce of a location before a shoot to take photos and figure out what kind of lights I would need as well as any other specialist or unusual equipment. But this time there simply wasn’t time. We would be shooting the same week and it was already a very busy week for me.

The next step before any shoot for me is some degree of planning. I like to have a concept for the video, at the very least some outline of the shots I need to tell the story, perhaps not a full storyboard, but at least some kind of structure. Once you have figured out the shots that you want to get you can then start to think about what kind of equipment you need to get those shots. In this case, as we would be shooting static works of art I felt that having ways to move the camera would really enhance the video. I have a small Jib as well as some track and a basic dolly that is substantial enough to take the weight of a fully configured PMW-F5 so these would be used for the shoot (I’m also now looking for a slider suitable for the F5/F55 that won’t break the bank, so let me know if you have any recommendations).

My PMW-F5 with Fujinon MK18-55mm zoom fitted with Duclos FZ mount.

So the first items on my kit list after the camera and lenses (the lenses were fitted with Duclos FZ rear mounts) was the jib and dolly. To achieve a nice shallow depth of field I planned to shoot as close to the lenses largest aperture of T2.9 as possible. This presents 2 challenges. The F5’s internal ND filters go in 3 stop steps – that’s a big step and I don’t want to end up at T5.6 when really I want T2.9, so 1 stop and 2 stop ND filters and my gucchi wood finished Vocas matte box would be needed (the wood look does nothing to help the image quality, but it looks cool). Oh for the FS7 II’s variable ND filter in my F5!

The second problem of shooting everything at T2.9 with a super 35mm sensor is that focus would be critical and I was planning on swinging the camera on a jib. So I splashed out on a new remote follow focus from PDMovie as they are currently on offer in the UK. This is something I’ve been meaning to get for a while. As well as the remote follow focus I added my Alphatron ProPull follow focus to the kit list. The Fujinon MK lenses have integrated 0.8 pitch gears so using a follow focus is easy. I now wish that I had actually purchased the more expensive PDMovie follow focus kit that has 2 motors as this would allow me to electronically zoom the lens as well as focus it. Oh well, another thing to add to my wish list for the future.

One other nice feature of the Fujinon MK’s is that because they are parfocal you can zoom in to focus and then zoom out for the wider shot and be 100% sure that there is no focus shift and that the image will be tack sharp. Something you can’t do with DSLR lenses.

The PDMovie follow focus motor engages perfectly with the pitch gears on the Fujinon MK series lenses.

Lighting: This was a daylight shoot. Now I have to say that I am still a big fan of old school tungsten lighting. You don’t get any odd color casts, it gives great skin tones, it’s cheap and the variety and types of lamp available is vast. But as we all know it needs a lot of power and gets hot. Plus if you want to mix tungsten with daylight you have to use correction gels which makes the lights even less efficient. So for this shoot I packed my Light and Motion Stella lamps.

Light and Motion Stella lamp fitted with 25 degree fresnel lens.

The Stellas are daylight balanced LED lamps with nice wide 120 degree beams. You can then use various modifiers to change this. I find the 25 degree fresnel and the Stella 5000 a particularly useful combination. This is the equivalent to a 650W tungsten lamp but without the heat. The fresnel lens really helps when lighting via a diffuser or bounce as it controls the spill levels making it easier to control the overall contrast in the shot. The Stella lights have built in batteries or can be run from the mains. They are also waterproof, so even if it rained I would be able to have lights outside the workshop shining in through the windows if needed.

I always carry a number of pop-up diffusers and reflectors of various sizes along with stands and arms specifically designed to hold them. These are cheap but incredibly useful. I find I end up using at least one of these on almost every shoot that I do. As well as a couple of black flags I also carry black drapes to place on the floor or hang from stands to reduce reflections and in effect absorb unwanted light.

Atomos Shogun Flame being used to check exposure and focus.

To check my images on set I use an Atomos Shogun Flame. Rather than mounting it on the camera, for this shoot I decided to pack an extra heavy duty lighting stand to support the Shogun. This would allow my assistant to use the flame to check focus while I was swinging the jib. The HDR screen on the Shogun allows me to see a close approximation of how my footage will look after grading. It  also has peaking and a zoom function to help with focussing which was going to be essential when the camera was up high on the jib and being focussed remotely. I also included a TV-Logic LUM171G which is a 17″ grading quality monitor with 4K inputs. The larger screen is useful for focus and it’s colour accuracy helpful for checking exposure etc.

For audio I packed my trusty UWP-D wireless mic kit and a pair of headphones. I also had a shotgun mic and XLR cable to record some atmos.

As well as all the larger items of kit there’s also all the small bits and bobs that help a shoot go smoothly. A couple of rolls of gaffer tape, crocodile clips, sharpies, spare batteries, extension cables etc. One thing I’ve found very useful is an equipment cart. I have a modiffied rock-n-roller cart with carpet covered shelves. Not only does this help move all the kit around but it also acts as a desk on location. This is really handy when swapping lenses or prepping the camera. It can save quite a bit of time when you have a mobile work area and somewhere you can put lenses and other frequently used bits of kit.

The day before the shoot I set everything up and tested everything. I checked the backfocus adjustment of the lenses. Checked the camera was working as expected and that I had the LUT’s I wanted loaded into both the camera and the Gratical viewfinder. With the camera on the jib I made sure I had the right weights and that everything was smooth. I also checked that my light meter was still calibrated against the camera and that the lens apertures matched what I was expecting (which they did perfectly). Color temperature and colorimetry was checked on the TVLogic monitor.

It’s worth periodically checking these things as there would be nothing worse than rocking up for the shoot only to find the camera wasn’t performing as expected. If you rent a cinema camera package from a major rental house it would be normal to set the camera up on a test bench to check it over before taking it away. But it’s easy to get lazy if it’s your own kit and just assume it’s all OK. A full test like this before an important shoot is well worth doing and it gives you a chance to set everything up exactly as it will be on the shoot saving time and stress at the beginning of the shoot day.

On the morning of the shoot I loaded up the car. I drive a people carrier (minivan to my friends in the USA). Once you start including things like a jib, track and dolly, equipment cart, 6x tungsten lights, 4 x LED lights, plus camera, tripods (including a very heavy duty one for the jib) the car soon fills up. A conventional saloon would not be big enough! One word of caution. I was involved in a car crash many years ago when the car rolled over. I had camera kit in the back of the car and the heavy flight cases did a lot of damage crashing around inside the car. If you do carry heavy kit in the car make sure it’s loaded low down below the tops of the seats. You don’t want everything flying forwards and hitting you on the back of your head in a crash. Perhaps consider a robust steel grill to put between the cargo compartment and the passenger compartment.

On arrival at the location, while it’s very tempting to immediately start unloading and setting up, I like to take a bit of a break and have a tea or coffee first. I use this time to chat with the client or the rest of the crew to make sure everyone knows what’s planned for the day. Taking a few minutes to do this can save a lot of time later and it helps everyone to relax a little before what could be a busy and stressful day.

Now it’s time to unpack and setup. I find it’s better to unpack all the gear at this time rather than stopping and starting throughout the day to unpack new bits of kit. Going to the car, unlocking, unpacking, locking, back to the set etc wastes time. This is where the equipment cart can be a big help as you can load up the cart with all those bits and pieces you “might” need… and inevitably do need.

The blacksmiths workshop. A small dark space.

The blacksmiths workshop was a dark space about 6m x 5m with black walls, open on one side to the outside world.  Blacksmiths forges (so I learnt) are dark so that the blacksmith can see the glow of the metal as it heats up to gauge it’s temperature. On the one hand this was great – huge amounts of relatively soft light coming from one direction. On the other hand the dark side was very dark which would really push the camera and lenses due to the extreme contrast this would create.

The seven blacksmithing processes. Frame grab from the film.

We set the jib up inside the workshop to shoot the various processes used by a blacksmith when working with iron and steel. Apparently there are only 7 different processes and anything a blacksmith does will use just these 7 processes or variations of them.

A small jib was used for much of the shoot.

Most of the shots done on the jib would be shot using the Fujinon MK18-55mm, so that’s the lens we started with. For protection from flying sparks a clear glass filter was fitted to the lens. While the finished film would be a 24p film, most of the filming was 4K DCI at 60fps recording to 16 bit raw. This would give me the option to slow down footage to 24p in post if I wanted a bit of slow motion.

When we did need to do a lens swap it was really easy. The Vocas matte box I have is a swing-away matte box. So by releasing a lever on the bottom of the matte box it swings out of the way of the lens without having to remove it from the rods. Then I can remove the lens and swap it to the other lens. The MK50-135mm is the same size as the MK18-55mm. The pitch gears are also in the same place. So swapping lenses is super fast as the follow focus or any focus motors don’t need to be re-positioned and the matte box just swings back to exactly the same position on the lens. It’s things like this that really separate pro cinema lenses from DSLR and photography lenses.

My wood effect Vocas swing away matte box.

For exposure I used the cameras built in LUT’s and the 709(800) LUT. I set the camera to 800EI. I used a grey card to establish a base exposure, exposing the grey card at 43% (measuring the 709 level). I used a Zacuto Gratical viewfinder which has a great built in waveform display, much better than the one in the camera. I also double checked my light levels with a light meter. I don’t feel that it’s essential to use a light meter but it’s a useful safety net. The light meter is also handy for measuring contrast ratios across faces etc but again if you have a decent waveform display you don’t have to have a light meter.

For the next 3 hours we shot the various processes seen in the video. Trying to get a variety of different shot. But when each process is quite similar, usually involving the anvil and a large hammer it was difficult to come up with shots that looked different.

Getting ready for a close up on the Anvil.

In the afternoon we set up to shoot the interview sequence. The reason for doing this was to not only provide the narrative for the film but also to help show how the lenses reproduce skin tones. The Fujinon MK series lenses are what I would describe as “well rounded”.  That is, not too sharp but not soft either. They produce beautifully crisp pictures without the pictures looking artificially sharp and this really helps when shooting people and faces. They just look really nice.

Shooting the interview sequence.

For the interview shot I used one of the Stella 5000 lights with the 25 degree fresnel lens aimed through a 1m wide diffuser to add a little extra light to supplement the daylight. This allowed me to get some nice contrast across the blacksmiths face and nice “catch light” highlights in his eyes. In addition the little bit of extra light on his face meant that the back wall of the forge would appear just that bit darker due to the increased contrast between his face and the back wall. This is why we light…. not just to ensure enough light to shoot with, I had plenty of light, if I remember right I had a 1 stop ND in the matte box. But to create contrast, it’s the contrast that gives the image depth, it’s contrast that makes an image look interesting.

Last setup of the day shooting the metal artworks. Using a gold reflector and Stella 5000 lamp to add some punch and drama to the shots.

The final stage was to shoot the treasure chest and ornate jars that would show off the the lenses macro and close up performance. The treasure chest is a truly amazing thing. It weighs around 80kg. The locking mechanism is quite fascinating and I still struggle to believe that it was all hand made. The small metal jars are made out of folded and welded steel. It’s the folds in the metal that create the patterns that you see.

Once again we used the jib to add motion to the shots. I also used the macro function of both the MK18-55mm and MK50-135mm lenses. This function allows you to get within inches of the object that you are shooting. It’s a great feature to have and it really adds to the versatility of these lenses.

The Zacuto Gratical has a much better waveform display than the cameras own, so it’s a useful viewfinder to have.

We wrapped at 7pm. Time to pack away the kit. It’s really important not to rush at this stage. Like everyone else I want to get home as quick as I can. But it’s important to pack your kit carefully and properly. There is nothing more annoying than when you start prepping for the next shoot finding that something has been broken or is missing because you rushed to pack up at the end of the previous shoot. Once you have packed everything away don’t forget to do that last walk through all the locations you’ve shot in to make sure you haven’t forgotten something.

I shot a little over hour of material. As it was mostly 60p 4K raw that came to about 1.5TB This was backed up on site using a Nexto-DI NSB25 which is a stand alone device that makes 2 verified copies of everything on 2 different hard drives. The film was edited using Adobe Premiere CC which handles Sony’s raw very easily. Grading was completed using DaVinci Resolve. I spent 2 days editing and a day grading the first version of the film. Then I spent another day re-grading it for HDR and producing the different versions that would be needed. All in, including coming up with the concept, finding the location, prepping, shooting and post took it took about 7 to 8 full work days to put this simple 4 minute film together.

Here’s the behind the scenes video 

cinematography, PXW-FS5, Shooting Tips, shoots, Workflow

Why is exposing log brightly beneficial?

6 Comments

I have been asked whether you should still expose log a bit brighter than the recommended base levels on the Sony PXW-FS5 now that Sony have released new firmware that gives it a slightly lower base ISO. In this article I take a look at why it might be a good idea to expose log (with any camera) a bit brighter than perhaps the manufacturer recommends.

There are a couple of reasons to expose log nice and bright, not just noise. Exposing log brighter makes no difference to the dynamic range. That’s determined by the sensor and the gain point at which the sensor is working. You want the camera to be at it’s native sensitivity or 0dB gain to get that maximum dynamic range.

Exposing brighter or darker doesn’t change the dynamic range but it does move the mid point of the exposure range up and down.  Exposing brighter increases the under exposure range but decreases the over exposure range. Exposing darker decreases the under exposure range but increases the over exposure range.

Something that’s important when thinking about dynamic range and big dynamic ranges in particular is that dynamic range isn’t just about the highlights it’s also about the shadows, it isn’t just over exposure, it’s under exposure too, it’s RANGE.

So why is a little bit of extra light often beneficial? You might call it “over exposure” but that’s not a term I like to use as it implies “too much exposure”. I prefer to use “brighter exposure”.

It’s actually quite simple, it’s about putting a bit more light on to the sensor. Most sensors perform better when you put a little extra light on them. One thing you can be absolutely sure of – if you don’t put enough light on the sensor you won’t get the best pictures.

Put more light on to the sensor and the shadows come up out of the sensors noise floor. So you will see further into the shadows. I’ve had people comment that “why would I ever want to use the shadows, they are always noisy and grainy”? But that’s the whole point – expose a bit brighter and the shadows will be much less noisy, they will come up out of the noise. Expose 1 stop brighter and you halve the shadow noise (for the same shadows at the previous exposure).  Shadows are are only ever noise ridden if you have under exposed them.

This is particularly relevant in controlled lighting. Say you light a scene for 9 stops. So you have 9 stops of dynamic range but a 14 stop sensor. Open up the aperture, put more light on the sensor, you get a better signal to noise ratio, less noisy shadows but no compromise of any type to the highlights because if the scene is 9 stops and you have 14 to play with, you can bring the exposure up by a couple of stops comfortably within the 14 stop capture range.

Chart showing S-Log2 and S-Log3 plotted against f-stops and code values. Note how little data there is for each of the darker stops, the best data is above middle grey. Note that current sensor only go to +6 stops ove middle grey so S-Log2 and S-Log record to different peak levels.

Look at the above diagram of Sony’s S-Log2 and S-Log3 curves. The vertical 0 line in the middle is middle grey. Note how above middle grey the log curves are more or less straight lines. That’s because above the nominal middle grey exposure level each stop is recorded with the same amount of data, this you get a straight line when you plot the curve against exposure stops. So that means that it makes very little difference where you expose the brighter parts of the image. Expose skin tones at stop + 1 or stop +3 and they will have a very similar amount of code values (I’m not considering the way dynamic range expands in the scene you shoot as you increase the light in the scene in this discussion). So it makes little difference whether you expose those skin tones at stop +1 or +3, after grading they will look the same.

Looking at the S-Log curve plots again note what happens below the “0” middle grey line. The curves roll off into the shadows. Each stop you go down has less data than the one before, roughly half as much. This mimics the way the light in a real scene behaves, but it also means there is less data for each stop. This is one of the key reasons why you never, ever want to be under exposed as if you are underexposed you mid range ends up in this roll off and will lack data making it not only noisy but also hard to grade as it will lack contrast and tonal information.

Open up by 1 additional stop and each of those darker stops is raised higher up the recording curve by one stop and every stop that was previously below middle grey doubles the amount of tonal values compared to before, so that’s 8 stops that will have 2x more data than before. This gives you a nice fat (lots of data) mid range that grades much better, not just because it has less noise but because you have a lot more data where you really need it – in the mid range.

Note: Skin tones can cover a wide exposure range, but typically the mid point is around 1 to 1.5 stops above middle grey. In a high contrast lighting situation skin tones will start just under middle grey and extend to about 2 stops over. If you accidentally under expose by 1 stop or perhaps don’t have enough light for the correct exposure you will seriously degrade the quality of your skin tones as half of your skin tones will be well below middle grey and in the data roll-off.

Now of course you do have to remember that if your scene does have a very large dynamic range opening up an extra stop might mean that some of the very brightest highlights might end up clipped. But I’d happily give up a couple of specular highlights for a richer more detailed mid range because when it comes to highlights – A: you can’t show them properly anyway because we don’t have 14 stop TV screens and B: because highlights are the least important part of our visual range.

A further consideration when we think about the highlights is that with log there is no highlight roll-off. Most conventional gamma curves incorporate a highlight roll-off to help increase the highlight range. These traditional highlight roll-offs reduce the contrast in the highlights as the levels are squeezed together and as a result the highlights contain very little tonal information. So even after grading they never look good, no matter what you do. But log has no highlight roll-off. So even the very brightest stop, the one right on the edge of clipping contains just as much tonal information as each of the other brighter than middle grey stops. As a result there is an amazingly large amount of detail than can be pulled out of these very bright stops, much more than you would ever be able to pull from most conventional gammas.

Compare log to standard gammas for a moment. Log has a shadow roll-off but no highlight roll-off. Most standard gammas have a strong highlight roll-off. Log is the opposite of standard gammas. With standard gammas, because of the highlight roll-off, we normally avoid over exposure because it doesn’t look good. With Log we need to avoid under exposure because of the shadow roll-off, it is the opposite to shooting with standard gammas.

As a result I strongly recommend you never, ever under expose log. I normally like to shoot log between 1 and 2 stops brighter than the manufacturers base recommendation.

Next week: Why is a Sony camera like the FS7,F5 800 ISO with standard gamma but 2000 ISO in log and how does that impact the image?

 

cameras, cinematography, Shooting Tips, Uncategorized

Beware Exposing To The Right With Log.

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That may seem like quite a sensational headline – beware exposing to the right with log – but let me explain.

First of all, I’m not saying you can’t or shouldn’t expose to the right, all I am saying is beware – understand the implications.

First of all what is normally meant by exposing to the right? Well it’s a term that comes from the world of photography where you would use the cameras histogram to measure the exposure levels. Exposing to the right would normally mean setting the shutter speed and aperture so that the levels shown on the histogram are as far to the right as you can get them without going beyond the right side of the histogram. This would ensure a nice bright exposure with lots of light falling on the sensor, something that is normally highly desirable as you get a nice low noise picture once you have adjusted and processed it in your photo editing software.

You can expose to the right with a video camera too. However when shooting with Rec-709 or conventional gammas this can often result in nasty looking highlights thanks to the default knee settings, so it’s not normally a good idea for 709 and standard gammas.

With log or raw as there is no highlight roll off you can expose to the right and it should give you a nice bright exposure… or will it?????

The problem with exposing to the right is that you are exposing for the highlights in the scene. If shooting a low contrast or low dynamic range scene this isn’t going to cause any problems as exposing to the right will mean that everything in the scene is nice and bright.

But if shooting a high dynamic range scene, say an outdoor scene with bright clouds in the sky but large areas of shadow, the exposure will be optimised for the highlights. The mid range and shadows may end up too dark. On a sunny day if shooting a person with their back to the sun the sky could easily be 6 or 7 stops brighter than the skin tones. If you expose for the sky/highlights the skin tones will be 1 or 2 stops darker than the basic exposure level recommended for most  log curves.

(S-log2/3 has 14 stops. At the base exposure you have 6 stops above middle grey and 8 below. Skin tones are normally between 1 and 2 stops above middle grey. So if the sky/highlights are 6 stops above the skin tones, then exposing for the highlights will put the skin tones where middle grey should be, which is 1 stop under exposed and 2 stops below where I would normally like to see skin tones when shooting with log or raw).

The first thing a viewer will notice when they look at a scene with faces or people will be the skin tones. If these have been under exposed they will be grainy and less than ideal. The viewer will notice noise and grain and poor shadows long before they look at the brightest highlights. Shooting log and protecting the highlights or exposing to the right will often compromise the all important mid tones because you are exposing for the highlights, not the midrange. In addition exposing for highlights with a high dynamic range scene can often push the shadows down in level and they will end up noisy and grainy. The biggest issue with exposing to the right is that it’s extremely difficult to estimate how many stops there are between your mid tones and the highlights, so you never know quite where your mid tones are falling.

(Midtones – generally a white piece of paper or a 90% reflectivity white card would be considered to be the top end of the mid tones. Go down about 2.5 stops from white and you hit middle grey  (18% grey card). This range between middle grey and white is where skin tones, plants, most animals etc will be and it probably the most important part of most images).

An important consideration with log and raw is that there is no highlight roll off. Standard gammas (with the default knee found on almost every camera) , cinegammas, hypergammas etc all roll off the highlights. That is to say that as you approach the peak recording level the contrast is reduced as the highlights are squeezed together to try to extend the dynamic range. This reduction in contrast means that it is very difficult, if not impossible, to recover any nice, useable picture information out of anything close to the peak recording level. As a result with conventional gammas we tend to avoid over exposure at all costs as it looks nasty. This highlight roll off is one of the things that gives video the video look.

Log and raw don’t have this same kind of highlight roll off. The image gets brighter and brighter until it clips. With log the stop immediately below clipping contains just as much picture information as any other stop brighter than middle grey. With linear raw the stop just below clipping has more information than any other stop. As a result in post production there is a very large amount of data that can be pulled out of these highlights, even if they are a little clipped! So don’t worry about a few clipped highlights when shooting log. The other thing to remember is there is no TV or monitor that can show these highlights as they really are, so they will never look perfect anyway.

Another thing that happens when exposing to the right is that grading becomes harder than it needs to be. Because the separation between the mid tones and highlights will vary greatly depending on things like whether you are shooting into or away from the sun, when you expose to the right you mid tone brightness will be up and down all over the place. So in post production as well as adding the look that you want to your footage, you are also going to have to spend a lot of time matching the mid range exposure to balance skin tones etc from shot to shot.

Rather than exposing to the right what I recommend is exposing for the mid range. After all this is the important part of the image. To do this you need to use a diffuse reflective shade. The most commonly used shades are a 90% white card and/or an 18% reflectivity grey card – middle grey. Get the mid range right and in most cases the highlights will take care of themselves. Getting the mid range right might mean exposing the mid range  brighter than the recommended levels. But it’s the mid range we need to measure, not the highlights, this is the important part of the image.

90% white is an incredibly important level in the world of film and video. A typical piece of office paper reflects about 92-94% of the light falling on it. Office paper often uses brighteners and special chemicals to make it look bright and white. This white is the brightest diffuse surface you will likely ever see.  Anything brighter than this is normally going to be an actual source of light. The sky perhaps or a direct bounced reflection off a shiny, reflective surface such as the bodywork of a car. So anything brighter than 90% white would normally be considered to be a highlight and to us humans, highlights are visually less important than the mid range. This is why the knee on most video cameras kicks in at around 90%. Anything brighter than 90% is a highlight so the knee only effects highlights and leaves the all important mid range alone.

Middle grey is also very important because it’s a shade of grey that to most people looks to be half way between black and white. Skin tones fall roughly half way between middle grey and white. In addition if you average all the brightness levels within a typical scene the end result is typically very close to middle grey.  Light meters are calibrated to middle grey. The relationship between middle grey and white is fixed. White reflects 90%, middle grey 18%, no matter how bright the actual light source. So whether you are indoors, outside. Whether it’s sunny or overcast, white and middle grey will always be close to 2.5 stops apart. They are extremely useful fixed reference levels.

There are many ways to measure the brightness of a white or grey card. My preferred method is with a waveform display. But you could also use zebras (use a narrow zebra window if you can).  You can also use false colour. Unfortunately it’s very difficult to use a histogram to measure the brightness of a specific target. The histogram is a great measuring tool for photography, but less than ideal for video. If you can’t get a white/grey card out in front of the camera you could consider using a light meter. It’s also worth noting that skin tones sit just a little over half way between middle grey and white, so if you have no other reference you could simply place your skin tones a touch brighter than half way between the values you are targetting for middle grey and white.

Just to be clear: I do still recommend exposing Sony’s S-log2, S-log3 and raw between 1 and 2 stops brighter than the Sony base levels. But the key take-away is that it’s the mid range you need to measure and expose at this level. Exposing to the right using a histogram or waveform and just looking at the peaks and brightest parts of the image does not tell you what is happening in he mid range. Measure the mid range, not the peak brightness.

 

cameras, Shooting Tips, Workflow

Why you need to sort out your post production monitoring!

2 Comments

One of THE most common complaints I hear, day in, day out, is: There is banding in my footage.

Before you start complaining about banding or other image artefacts ask yourself one very simply, but very important question: Do I know EXACTLY what is happening to my footage within my computer or playback system? As an example, editing on a computer your footage will be starting of at it’s native bit depth. It might then be converted to a different bit depth by the edit or grading software for manipulation. Then that new bit depth signal is passed to the computers graphic card to be displayed. At this point it will possibly be converted to another bit depth as it passes through the GPU and then it will be converted to the bit depth of the computers desktop display. From there you might be passing it down an HDMI cable where another bit depth change might be needed before it finally arrives at your monitor at goodness knows what bit depth.

The two images below are very telling. The first is a photo of a high end TV connected to my MacBook ProRetina via HDMI playing back a 10 bit ProRes file in HD. The bottom picture is exactly the same file being played back out of an Atomos Shogun via HDMI to exactly the same TV. The difference is striking to say the least. Same file, same TV, same resolution. The only difference is the top one is playing back off the computer, the lower from a proper video player. I also know from experience that if I plug in a proper video output device such as a Blackmagic Mini-monitor to the laptops Thunderbolt port I will not see the same artefacts as I do when using the computers built in HDMI.

And this is a not just a quirk of my laptop, my grading suite is exactly the same. If I use the PC’s built in HDMI the pictures suck. Lots of banding and other unwanted artefacts. Play back the same clip via a dedicated, made for video, internal PCI card such as a Decklink card and almost always all of the problems go away. If you use SDI rather than HDMI things tend to be even better.

So don’t skimp on your monitoring path if you really want to know what your footage looks like. Get a proper video card, don’t rely on the computers GPU. Get a decent monitor with an SDI input and try to avoid HDMI for any critical monitoring.

Shot viewed on a good quality TV via HDMI from the computers built in graphics card. Notice all the banding.
Exactly the same shot/clip as above. But this time played back over HDMI from an Atomos Shogun Flame onto the very same TV. Not how all the banding has gone.

 

Shooting Tips, shoots

Watch your viewfinder in bright sunshine (viewfinders with magnifiers or loupes).

4 Comments

Just a reminder to anyone using a viewfinder fitted with an eyepiece, magnifier or loupe not to leave it pointing up at the sun. Every year I see dozens of examples of burnt  and damaged LCD screens and OLED displays caused by sunlight entering the viewfinder eyepiece and getting focussed onto the screen and burning or melting it.

It can only take a few seconds for the damage to occur and it’s normally irreversible. Even walking from shot to shot with the camera viewfinder pointed towards the sky can be enough to do damage if the sun is out.

So be careful, cover or cap the viewfinder when you are not using it. Tilt it down when carrying the camera between locations or shots. Don’t turn to chat to someone else on set and leave the VF pointing at the sun. If you are shooting outside on a bright sunny day consider using a comfort shade such as an umbrella or large flag above your shooting position to keep both you and the camera out of the sun.

Damage to the viewfinder can appear as a smudge or dark patch on the screen that does not wipe off. If the cameras was left for a long period it may appear as a dark line across the image. You can also sometimes melt the surround to the LCD or OLED screen.

As well as the viewfinder don’t point your camera directly into the sun. Even an ND filter may not protect the sensor from damage as most regular ND filters allow the infra red wavelengths that do much of the damage straight through.  Shutter speed makes no difference to the amount of light hitting the sensor in a video camera, so even at a high shutter speed damage to the cameras sensor or internal ND’s can occur. So be careful when shooting into the sun. Use an IR ND filter and avoid shooting with the aperture wide open, especially with static shots such as time-lapse.

 

A7, cameras, cinematography, PMW-F55, PXW, PXW-FS5, PXW-FS7, Shooting Tips, Technology

The great S-Log2 or S-Log3 debate.

21 Comments

I’ve written about this many times before, but still it comes up again and again. Which is better? Which should I use? I hear all kinds of crazy comments and a lot of incorrect information, so first of all lets dispel a few myths:

S-Log2 captures more dynamic range than S-Log3, it goes to a higher level on the waveform, S-Log3 clips the highlights sooner.

On most of Sony’s current cameras S-Log2 and S-Log3 both currently record exactly the same dynamic range as this is limited by the sensors that Sony are using. The S-log3 curve could be used in a future camera to capture up to 16 stops and in fact the new Venice camera records over 15 stops.  But as all of Sony’s other cameras sensors can only see 14 stops and the S-Log3 curve is designed to go beyond 14 stops, stop No. 14 is not recorded all the way at the top of the recording range.  S-Log2 is a 14 stop maximum curve, so the peak level is recorded right at the top of the recording range. There is no space held in reserve for anything beyond 14 stops.

In Sonys current camera range (other than Venice) the limit is 14 stops whether it’s S-Log2 or S-Log3. The chart that Sony provide showing both S-Log2 and S-Log3 is a little confusing as it shows the entire gamma curve rather than what the camera can actually “see”. In their current implementations both curves stop at +6 stops over middle grey, both capture the same dynamic range, there is no difference.

S-Log2 is brighter than S-Log3 so it must be capturing highlights better.

No, not really, see above. Playback and on screen brightness comes from the levels chosen to record something at and is dependant on the shape and range of the gamma curve. But the actual captured range is dependant on what the sensor can cope with. As we are not changing the sensor, the captured dynamic range, brightness range and shadow range does not change between S-Log2 and S-log3, both of which take the entire sensor range (they just store that same range using slightly different levels or code values). After applying a LUT or other conversion to your normal viewing gamma both S-Log2 and S-log3 will have the same brightness, same highlight and same shadow range.

S-Log3 has noisy shadows.

No, not really. Shadows appear noisy with S-Log3 as the shadow part of the curve is stored using higher code values compared to S-Log2. So when you view S-Log3 uncorrected the shadows are raised and stretched on your conventional monitor and this gives the impression of a noisy picture. In reality once you restore the levels to normal there is no additional noise. See this article for a full explanation.

Chart showing S-Log2 and S-Log3 plotted against f-stops and code values. Note how little data there is for each of the darker stops, the best data is above middle grey. Note that current sensors only go to +6 stops over middle grey so S-Log2 and S-Log record to different peak levels.

S-Log3 is newer than S-Log2 so it must be better.

Newer, perhaps not. Better, no not really. S-Log3 is based on the industry standard Cineon log gamma curve. This curve was developed in the 1980’s to allow the digitising of film using 10 bit data. So S-Log3 matches a curve designed to work with negative film and is capable of storing more than the 14 stops that most of the current cameras sensors can see. In effect it is an old log gamma curve. As it is a curve designed for more than 14 stops, when used in a 14 stop camera some of the available recording data is empty and wasted.

S-Log2 was specifically designed by Sony to work with an electronic sensor with 14 stops of dynamic range and is optimised to match the performance characteristics of video sensors. By using a 14 stop curve with a 14 stop camera almost every bit of available data is utilised, there is no wastage. So S-Log2 makes better use of the data you have available to you,

BUT THERE ARE SOME OTHER FACTORS WE NEED TO CONSIDER.

S-Log2 and S-Gamut:

As well as the gamma curve we also have different Gamuts or color ranges. S-Log2 was originally designed for the F65 camera. The F65 sensor can capture a huge color range beyond the range that most conventional video sensors can see. So as well as S-Log2 Sony introduced S-Gamut which was matched to the very wide color range of the F65 sensor. S-Log2 is designed to be used with S-Gamut. But many of the cameras we use, like the FS7, F5, FS5 cannot see this color range (Sony’s F55 and Venice can). In addition this very large color range can be a little tricky to deal with in post production. Add to this the fact that S-Log2 is quite different to the quite common Cineon gamma curve and behaves differently to other curves in post. The end result was that in the early days of S-Log2 there were a number of complaints and comments that Sony’s S-log2 material was difficult to grade.

S-Log3 and S-Gamut3.

Because some people were struggling a bit with S-Gamut and S-Log2 in post production (Resolve and many of the other tools we have today were not as well developed 4 years ago), Sony introduced S-Gamut3 and S-log3 as well as a further Gamut called S–Gamut3.cine. S-Log3 was based on Cineon as that’s what people were familiar with. Arri’s Log-C is also based on Cineon as are many other log curves. This makes it a more “familiar” grading experience for many colorists. In addition Sony created a modified version of the super large S-Gamut to make it easier to grade.  S-Gamut3 is just as big as S-Gamut but some tweaks inside make it easier to grade (fewer color shifts). At the same time Sony realised that most users were producing content for TV, the web or digital cinema that had little use for the huge color range of S-Gamut/S-Gamut3.  So S-Gamut3.cine was developed as a smaller, more manageable version of S-Gamut3 and it incorporated a few tweaks to the color science to provide colors closer to those used by other manufacturers. S-Gamut3.cine is also a better match for cameras with sensors that cannot see the full S-Gamut range (like the FS5, FS7, F5, A7).

The end result is that in general most people prefer or find it easier to grade S-Log3/S-Gamut3.cine material than S-Log2/S-Gamut. Plus you can often use LUT’s designed for Log-C or Cineon with S-log3 material (this isn’t optimum, but it can work).

SGamuts Compared.

Getting the data from camera to post.

In terms of getting the data from your cameras sensor in to post production S-Log2 is the better choice (unless you have a Sony Venice which only has S-Log3). S-Log2 is optimised for the way an electronic sensor works. S-log3 is essentially a curve designed for negative film applications, not video and no matter how you look at it, these are electronic video cameras. However, if you are recording 10 bit or greater you have a lot of data whichever curve you use, so in practice it will be rare to see any difference in the final result.

So use the curve you find easiest to work with. It is true that S-Log 3 allocates a little more data to the shadows and less to the highlights than S-Log2, but don’t confuse data and code values with more range. S-Log3 has a few extra code values in it’s darkest stops, S-log2 has a few extra in the bright stops, but the dynamic range, highlight and shadow handling is governed by the sensor not the gamma curve. Overall S-Log3 has fewer code values than S-Log2, S-Log2  makes better use of the data available, but with 10 bit this really isn’t going to make a huge difference.

8 Bit Recording.

But if you are only recording with an 8 bit codec you are already at a disadvantage. When recording 8 bit you really need to maximise the way what little data you have is used. For that reason I will always recommend that S-Log2 is used when recording 8 bit on a camera like the FS5 in UHD or A7s or similar (FS5 is 10 bit in HD). By using S-Log2 you are using as many of the limited code values available as you can. This doesn’t mean you can’t use S-log3, it just wouldn’t be my choice.

The end result should be the same.

At the end of the day, if you were to use matching LUTs, S-log2 and S-log3 material should look more or less exactly the same after grading or application of the LUT, no matter what the scene you are shooting. If they do look significantly different then you are doing something wrong. So your choice of curve, other than for 8 bit recordings will most likely come down to ease of use rather than anything else.

If your camera doesn’t have LUT’s then S-Log2 can be easier to work with as it is more contrasty. This makes it a bit easier to focus and also makes it easier to gauge exposure. If your camera has LUT’s and you use them, then you may decide to use S-Log3 simply because you should find it a little easier to work with in post. Either way both curves capture the same range of picture information and both should give more or less the same end result.

There may be some very, very subtle differences due to the small differences in data distribution, but often these will be hard to really see in the final image.

cameras, Shooting Tips, Technology, Workflow

Notes on Timecode and Timecode Sync for cinematographers, part 2.

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In the first part of this 2 part article we saw how at some frame rates timecode will drift relative to a real time clock (Click Here for part 1). As well as drifting relative to real time due to the way timecode can only count the actual whole frames recorded,  the internal clocks that govern the timecode generators in many devices may drift slightly over time.

For single camera operation this drift is rarely significant but as soon as you start using multiple cameras or recording sound separately to the camera, even very small differences of just a frame or two between each device can cause problems. A one frame error is enough to cause a visible lip sync error, by two frames the sync error is pretty obvious to most people.

So, very often we need to synchronise the timecode across multiple devices so that the audio timecode matches the camera timecode or multiple cameras all have the same timecode so that it’s easy to re-align everything in post production. Most professional video cameras will have a timecode in or timecode out connector and the simplest way to sync two cameras is to feed the timecode from one cameras timecode out to the other cameras timecode in. For this to work both cameras must be set to “Free Run” timecode.

BUT YOU ALSO NEED GENLOCK OR SYNC LOCK

This is the part that often gets overlooked. If you read the first part you should understand that when a video camera is recording the timecode is generated by counting the number of frames recorded. As a result the precise frame rate of the camera will determine how many frames are recorded in any given time period and as a result the timecode for that clip. When you press the record button to start a recording the cameras timecode will match any external timecode fed to the camera. But from that point forward until the end of the recording the timecode just counts the frames recorded and will ignore any external timecode.

So the only way to ensure 100% accurate timecode sync between multiple cameras or between a camera and some other external timecode source is by providing not only a common timecode source but also a sync source that is locked to the timecode. By feeding the camera sync that is locked to the timecode into the cameras genlock input the cameras frame rate will be locked to the master frame rate so you will not get any timecode drift.

It’s amazing how many people overlook the fact that a cameras timecode generator counts frames while recording, so if the cameras frame rate is a tiny bit off, even with an external timecode source it will drift. It’s only by synchronising the camera through sync and genlock that you can be sure to eliminate any timecode drift.

SYNC SOUND:

If you are recording sound remotely from the camera you need to keep the camera and audio recorders timecode in sync. The timecode in a camera is dependant on the actual frames recorded while the timecode on an audio recorder is often nothing more than a data or audio track that records the timecode signal. It is rarely locked to the recorders sampling or recording rate. Because of this the correct way to link the timecode in this scenario is from the camera to the recorder.

If you do it the other way around (which for some reason appears to be the most common way) you cannot be sure that you won’t get timecode drift unless the audio recorder is also sending sync to the cameras genlock input. Normally a small amount of drift will go un-noticed on shorter shots. The cameras timecode will re-sync with the external timecode when you stop recording, so the beginning of each shot will have the correct timecode. As a result you will normally get away with feeding timecode only from an audio recorder.  But on longer takes, say shooting a music event it can become a significant issue as the camera and recorder drift apart over longer takes.

23.98fps.

As you should have learnt from part one, 23.98fps timecode can be particularly difficult to deal with as the timecode in a camera shooting at 23.98fps will always drift by 3.6 seconds an hour relative to real time. So be very, very careful if shooting 23.98fps but using an audio recorder that uses a real time clock. There is no way to satisfactorily sync a real time clock with a camera shooting 23.98fps. Over the course of a 1 minute clip you will see the timecode drift by over 1 frame. If you wish to do sync sound at 23.98fps you need to ensure your audio recorder supports either 23.98fps timecode or at a push Non Drop Frame 29.97fps timecode. You can only sync 23.98fps tmecode with 23.98fps timecode, but a free running, Non Drop Frame 29.97fps recorder should stay closer in sync than a real time clock.

If your audio recorder only has a real time clock I strongly suggest shooting at 24fps rather than 23.98fps where you can. 24fps is a whole number so 24fps timecode does not drift by 3.6 seconds per hour compared to real time. So any sync issues should be much reduced at 24fps compared to 23.98fps. If shooting 29.97fps (often mistakenly referred to as 30fps/60i) then you should use Drop Frame Timecode when working with recorders with a real time clock.

WHAT IF THE CAMERA DOESN’T HAVE TC IN?

There are a few pro cameras that don’t have a dedicated timecode in or timecode out port. The very popular Sony PXW-FS7 does not have timecode in and can’t be genlocked unless you add the optional extension unit to the camera. For cameras such as these, if you need to record sync sound on a separate recorder one option is to record the timecode output from the audio recorder as an audio signal on one of the cameras audio tracks. Timecode recorded on an audio track like this will rarely line up perfectly with the cameras own internal timecode so it should never be used as the main timecode for the recorded video. But there are plenty of software tools that will allow you to read this timecode in post production so that you can use it to line up your audio recordings with the video recording. This isn’t an ideal solution, but it’s better than relying on two different clocks, one in the camera, one in the recorder possibly running at quite different rates.

MULTICAMERA SHOOTS.

If you have multiple cameras or audio recorders it may be possible to loop the time code (and hopefully sync too) from camera to camera, so that every device is connected. Another option is to use a single master timecode and sync source and hard wire every camera to that. The problem with either of these is that if the venue is large you need a lot of cable. Sometimes it simply isn’t possible to use cables to connect everything together so instead of cables we connect the cameras wirelessly.

WIRELESS.

Wireless timecode connections normally work OK. If you momentarily loose the wireless timecode link the cameras timecode clock will just keep counting the frames recorded without issue. But as we have already seen, for true drift free timecode lock we also need to synchronise the camera via genlock. Sending genlock wirelessly is not normally a good idea. Any interruption of the sync signal will cause the cameras frame rate to jitter and that’s really bad. In practice it is quite common to link the timecode of several devices wirelessly without sync. Again for shot takes this is often perfectly OK. The lack of sync however can be an issue on longer takes. A good example of this would be a music concert where it really is vital that all the cameras and recorders run in sync.

Companies such as Ambient have wireless timecode and sync devices where each of the sync boxes (lockit box) has it’s own very high precision, temperature compensated sync clock.  All the boxes then sync to one master device, should the wireless signal drop out the internal sync clocks will continue to provide both a genlock sync pulse and timecode that is so precise that you should not see any timecode or sync drift over several days.

If you missed part 1 you can find it by clicking here.