How much technology does a modern cinematographer need to know?

This post might be a little controversial, I am often told “you don’t need to know the technical stuff to be a cinematographer” or “I don’t need to know about log and gamma, I just want to shoot”.

I would argue that unless you are working closely with a good DIT a modern DP/Cinematographer really does need to understand many of the technical aspects of the equipment being used, in particular the settings that alter the way the camera captures the images. Not just things like “set it to gamma x for bright scenes” but why you would want to do that.

Now I’m not saying that you have to be a full blown electronics engineer, but if you really want to capture the best possible images it really is very important that you truly understand what the camera is doing. It’s also a huge help to understand how your footage will behave in post production. Any craftsman should understand the correct way to use his tools and not only know how to use them but how they work.

Part of the understanding of how your chosen camera behaves comes from testing and experimentation. Shooting test clips across a range of exposures, trying different gamma or log curves and then taking the footage into post production and seeing how it behaves.

Film cinematographers will shoot tests with different film stocks before a large production under the kinds of lighting conditions that will be encountered during the film. Then the film would be processed in different ways to find the best match to the look the cinematographer is trying to achieve. Digital cinematographers should be doing the same and importantly understanding what the end results are telling them.

Most of the great painters didn’t just pick up a paint brush and slap paint on a canvas. Many artists from  Da Vinci to Turner studied chemistry so they could develop new paints and painting techniques. DaVinci was a pioneer of oil painting, Turner used to make his own paints from base pigments and chemicals and patented some of the unique colors he created.

This doesn’t take anything away from the traditional skills of lighting and composition etc, those are just as important as ever and always will be. But modern electronic cameras are sophisticated devices that need to be used correctly to get the best out of them.  I believe that you need to understand the way your camera responds to light. Understands it’s limitations, understand it’s strengths and learn how to use those strengths and avoid the weaknesses.

And that’s a really important consideration. Today the majority of the cameras on the market are capable of making great images…… Provided you know how to get the best from them. One may be stronger in low light, one may be better in bright light. It may be that one camera will suit one job or one scene better than another. You need to learn about these differences and understanding the underlying technologies will help you figure out which cameras may be candidates for your next project.

It’s not just the camera tech that’s important to understand but also how to manage the footage all the way from the camera to delivery. While you don’t need to be an expert colorist, it certainly helps if you know the process, just as film cameramen know about color timing and film processing. A trend that is growing in the US is high end cinematographers that also grade.

This has come about because in the days of film the cinematographer could determine the look of the finished production through a combination of lighting, the choice of film stock and how it was to be processed. Today a cinematographer may have much less control  over the final image as it passes through the post production and grading process. Often the final look is determined by the colorist as much as the cinematographer. By also becoming colorists and staying with their material all the way through post production, cinematographers can retain control of the final look of the production.

As HDR (High Dynamic Range) delivery becomes more important along with the need to deliver SDR content at the same time, a good understanding of the differences between and limitations of both systems will be needed as you may need to alter the way you expose to suit one or the other.

So, there is lots that you need to know about the technology used in todays world of digital cinematography. Where there is a big enough budget DIT’s (Digital Imaging Technicians) can help cinematographers with guidance on camera setups, gamma, color science, LUT’s and workflows. But at the low budget end of the market, as a cinematographer you need at the very least a firm grasp of how a modern camera works, how to correctly mange the dat it produces (you would be amazed how many people get this wrong). Finally how the material handles in post production, if you really want to get the best from it.

It isn’t simple, it isn’t always easy, it takes time and effort. But it’s incredibly rewarding when it all comes together and results in beautiful images.

If you disagree or have your own take on this please post a comment. I’d love to hear other views.

Caution with new type 128GB XQD cards in the PMW-F5 and F55 (maybe others too).

xqd-new Caution with new type 128GB XQD cards in the PMW-F5 and F55 (maybe others too).
New, faster G series XQD cards that may be causing problems in some cameras.

UPDATE – IT IS NOW CONFIRMED THAT THE NEW 440MB/s CARDS WILL NOT WORK UNDER V7 OR EARLIER FIRMWARE. A FIX WILL BE INCLUDED IN VERSION 8.

There have been some comments on an older thread about problems with the very latest slightly faster Sony G series 128GB XQD cards with Sony’s F5 and F55 cameras (thanks Justin and Richard).

Many people, including myself use XQD cards with the Sony QDA-EX1 adapter in the PMW-F5 and PMW-F55 as well as other SxS cameras. Up to now I’ve never heard of any real problems, basically they work pretty much the same as SxS cards.

Very recently Sony released a new very slightly faster XQD cards. The old cards have a maximum write speed of 350MB/s while the new cards have a max write speed of 440MB/s. You can see in the image above of one of the new cards that both the read and write speeds are shown on the front of the card. The old (good) cards only show a single speed (400MB/s).

From what I have been able to gather so far the old 128GB G series cards work just fine, but a few people are reporting that the new faster 128GB ones do not. Problems include being unable to format the cards in the camera or unable to write anything to the cards.

If you have any experience of this issue, good or bad, with the new 64GB or 128GB 440MB/s cards please let me know by adding a comment.

 

Training Videos for the PXW-FS5 and PXW-FS7

Just a reminder that the full sets of traing films for the PXW-FS5 and the PXW-FS7 are available for viewing for free on YouTube.

The FS7 videos can be found by following this playlist link.

There are 10 videos taking you from basic setup all the way through scene files, cine EI and the effects shooting modes.

There are currently 2 PXW-FS5 videos.

The first on picture profiles and picture settings is here.

The second on the advanced shooting modes is here.

I am currently working on a further video on using the FS5’s raw output and this should be available in the next couple of weeks.

Don’t forget if you have any questions I have my Webinar day coming next week.

 

Free Webinar Day – July 26th 2016.

4K – It’s not the be-all and end-all.

I often hear people talking about future proofing content or providing the best they can for their clients when talking about 4K. Comments such as “You’d be crazy not shoot shoot 4K for a professional production”. While on the whole I am a believer in shooting in 4K, I think you also need to qualify this by saying you need to shoot good 4K.

As always you must remember that bigger isn’t always better. Resolution is only one part of the image quality equation. Just take a look at how Arri’s cameras, the Alexa etc, continue to be incredibly popular for high end production even those these are in effect only HD/2K cameras.

Great images are a combination of many factors and frankly resolution comes some way down the list in my opinion. Just look at how DVD has managed to hang on for so long, feature films on DVD still look OK even though the resolution is very low. Contrast and dynamic range are more important, good color is vital and low noise and artefact levels are also essential.

A nice contrasty image with great color, low noise and minimal artefacts up scaled from HD to 4K may well look a lot better than a 4K originated image that lacks contrast or has other artefacts such as compression noise or poor color.

So it’s not just about the number of pixels that you have but also about the quality of those pixels. If you really want to future proof your content it has to be the best quality you can get today, not just the largest you can get today.

Free Webinar Day – July 26th 2016.

On Tuesday the 26th of July I will be hosting a series of free live webinars giving you the chance to ask me questions about many of the things I write about here. This is a trial run, I’ve done webinars for many people in the past and they have always gone down well, but these webinars are going to come live from xdcam-user HQ.

If they are a success I will make this a regular event with a webinar day once a month with new subjects covered each time as well as an open Q&A session.  This will give you the chance to ask questions on any aspect of video production, so start thinking about what you want to ask.

If you haven’t attended a webinar before here is how it works: You log in online to the webinar using the link provided. You will hear me and any guest presenters and see any pre-prepared information slides that I have on your computer/tablet/phone screen.  You ask questions by typing them into a question box, nobody will see or hear you. I will try to respond to as many questions as I can within the one hour time limit. The session will also be recorded and can be downloaded later if you wish. There are dedicated online versions of the webinar page for computers, tablets and smart phones, so you should be able to log in almost anywhere where you have an internet connection.

There will be 2 webinars where I will take questions on any of the Sony large sensor cameras, including the FS5, FS7, F5 and F55.  If you want to know about settings, exposure, LUT’s, slow mo, lenses or anything else you can ask me on the 26th. These are timed so that there is an opportunity for people in most countries around the world  to join one or the other at a sensible time of day.

Click on the appropriate link below to register.  Please only register for sessions you will actually attend as numbers are restricted.

Session 1: Ask anything about the FS5, FS7, F5 and F55. Tuesday July 26th, 8am – 9am GMT. (9:00 BST, 10:00 CET,  12:00 Dubai, 13:30 Delhi, 16:00 Singapore, 18:00 Sydney).

Session 2: Ask anything about the FS5, FS7, F5 and F55. Tuesday July 26th, 18:00 – 19:00 GMT. (19:00 BST, 20:00 CET, 14:00 NYC, 11:00 LA).

HDR Session 1: What is HDR and what do I need to know? Tuesday July 26th,  10am – 11am GMT. (11:00 BST, 12:00 CET,  14:00 Dubai, 15:30 Delhi, 18:00 Singapore, 20:00 Sydney).

HDR Session 2: What is HDR and what do I need to know? Tuesday July 26th,  16:00 – 17:00 GMT. (17:00 BST, 18:00 CET, 12:00 NYC, 09:00 LA).

If you can’t attend I will make the recordings available after the day. If you think this is a good idea then please share this page so others can also join in.

Image quality with B4 ENG lenses on large sensor cameras.

DSC02056 Image quality with B4 ENG lenses on large sensor cameras.
2/3″ B4 lens on the FS700via the MTF adapter.

This is something that comes up a lot and I get many questions about. In part because I designed the MTF B4 to Canon, FZ and E-Mount adapters. Budget adapters that allow you to use a 2/3″ B4 ENG lens on a Super 35mm sensor by using the lenses 2x extender or on a center crop sensor without the 2x.

The question is… what will the pictures look like?

The answer is… it depends on the lens.

Not a very helpful answer perhaps, but that’s the truth of it. Different lenses perform very differently. For a start I would say forget 4K. At best these lenses are suitable for HD and you want to have a great HD lens if you want good HD pictures.

But what about the “look” of the images? My experience is that if you put a wide range ENG zoom on a S35mm camera the look that you get can be best described as “2/3″ ENG look with maybe shallow depth of field”. Lets face it, ENG lenses are full of compromises. To get those great big zoom ranges with par-focal focus there are a lot of glass elements in those lenses. Lot’s of elements means lots of places where CA and flare can occur. The end result is often a lowering of contrast and color fringing on hard edges, the very same look that we are used to seeing on 2/3″ cameras.  Typical cine or DSLR lenses tend to have simpler optical designs. Prime lenses are normally sharper and show better contrast with less flare than zooms due to there simpler internal design.

So don’t expect to put a typical B4 ENG lens on your S35mm camcorder and still have that crisp, high contrast digital cinema look. Of course B4 zooms are handy for the ability to zoom in and out through huge ranges while holding focus. So an adapter and lens may well make your S35mm camera more versatile. But if you want the best possible images stick to cine style lenses, DSLR lenses or zooms designed for S35.

 

Revealing Signal to Noise and Exposure experiment for PMW-F5, F55 and FS7.

Here’s a little experiment for you to try if you have a PMW-F5, PMW-F55 or PMW-FS7. It should help you understand a few key things about the way these cameras behave, notably:

1: Why ISO does not actually reflect the sensitivity of the camera.

2: Why it is beneficial to expose S-Log2 or S-Log3 brighter than the Sony recommended levels.

3: How to get the best possible S-Log footage.

4: Why S-log may be a poor choice for low light.

Ideally you will want to use an external waveform monitor connected to the cameras SDI output, but it is possible to use the built in waveform display.

Start with the camera in Custom mode. Choose “STD” gamma and Rec-709. Set the gain/ISO settings so that the camera is showing ISO.

Set the ISO to the base ISO (800 ISO on F5/FS7, 500 ISO on F55).

Expose a 90% white card so that white is 90% on the waveform display. This doesn’t need to be 100% accurate, you can use a piece of paper if you don’t have a proper white card. Don’t change the ISO/Gain, light the white card if you need to. Make a note of the aperture.

Now change the gamma selection to S-Log2, do not change the exposure.

Note how white now drops down to about 70% and also note that the ISO becomes 2000 ISO on an F5 or FS7 and 1250 ISO on an F55.

Think about this for a moment: If the ISO has gone up, how can white and the bulk of my image become darker?

Now switch the camera to show dB gain instead of ISO, the gain should be showing 0dB. Repeat the above switching from Standard 709 gamma to S-Log2 and note that the gain remains at 0dB for both rec-709 and S-Log2.

Think about this: The gain is the same for both 709 and S-log2 but the S-Log2 image is darker. As the gain is NOT changing then the sensitivity is not actually changing, so why does the ISO change?

If you were to use a light meter and start off with the light meter set to 800 (500) ISO the light meter would tell you to set the aperture to whatever it is you currently have to give the correct exposure in rec-709 with white at 90%.  If you had a light meter and you change the ISO setting on the light meter from 800(500)ISO to 2000(1250) ISO the light meter will tell you to close the aperture by 1.3 stops.

So, on your camera, while it is set to S-Log2 close the aperture from it’s original setting by 1.3 stops. Now you will find that white will be at the recording levels given by Sony for S-Log2 which is 59% for white and 32% for middle grey.

So what have we learnt from this? The gain is the same for both standard gamma and S-Log2, even though the ISO changes from 800(500) to 2000(1250) ISO. So the sensitivity and amount of noise coming from the sensor is the same in both cases. But the indicated ISO changes so that if you are using an external light meter, when you switch to S-Log the higher indicated ISO  will make the light meter tell you to close the aperture. This means there is less light falling on the sensor. This means that the recorded image will have a worse signal to noise ratio (noise remains the same, but signal is smaller).

To solution of course to this poorer signal to noise ratio is simply to open the aperture back up again by 1.3 stops. When shooting S-Log2 or S-Log3 using the CineEI mode I always recommend using 800EI on an F5 or FS7 or 640EI on an F55. This means your aperture becomes the same as it would be when shooting in vanilla Rec-709, the end result is the same, improved, signal to noise ratio. If you are not using CineEI or LUT’s, then expose white at 70%.

Understanding the all important “Signal to Noise Ratio”.

The Signal to Noise ratio is one of the key factors in determining the quality of a video or stills image. A noisy, grainy picture rarely looks as good as a low noise “clean” image. In addition it’s noise in your images will limit how far you can grade them before the picture quality becomes unacceptably poor.

Almost always what you want is the biggest possible signal with the least possible noise. In a video or film camera the signal is the desired image information or in simple terms the picture. While the noise is…. well….. the noise.

Once upon a time, when film cameras were normal for both still photography and film the noise in the pictures came primarily from the grain structure of the film stock. One of the great features of film cameras is that you can actually change that film stock to suit the type of scene that you are shooting. For low light you could use a more sensitive film stock that was actually truly more sensitive to light. However, often a very sensitive film stock will show more noise as the grain of more sensitive film is normally larger.

With video and digital stills cameras however things are quite different. You can’t normally change the sensor in a video camera and it’s the sensor that determines the sensitivity of the camera and it is the sensor that is the source of the majority of the noise.

Modern CMOS video sensors consist of two parts. The light gathering part and the readout part. The size of the pixels on a sensor is one of the key factors in determining the sensitivity and dynamic range. Small pixels are not good at capturing, converting and storing large numbers of photons of light or electrons of electricity.  Bigger pixels are much better at this, so big pixels typically mean better sensitivity and a better dynamic range. Each pixel is unique and as a result every pixel on the sensor will perform slightly differently. The signal stored in the pixels is a tiny analog signal that is easily disturbed by stray electric currents and variations in temperature. As a result of the small variations from pixel to pixel, the stray signals and heat, there is a small variation from moment to moment in the signal that comes off the pixel when it is read out and these variations are what we see as noise.

The analog signal from the pixels is passed to a circuit that converts it to a digital signal. The analog to digital conversion process normally includes some form of noise reduction circuitry to help minimise the noise. By carefully mapping the A to D circuity to the signal range the pixels provide, a sensor manufacturer can find the best combination of noise, dynamic and sensitivity. Once the signal has been converted to a digital one, the noise level, sensitivity and dynamic range is more or less locked in and can’t be changed (Some cameras have the ability to use slightly different A to D conversion ranges to help give improved noise levels at different brightness/dynamic ranges).

The bottom line of all this is that with the vast majority of video cameras the noise level is more or less fixed,  as is the sensitivity as we can’t actually swap out the sensor.

But wait! I hear you say…. My camera allows me to change the ISO or gain. Well yes it probably does and in both cases, ISO or gain, with a digital video or stills camera what you are changing is the cameras internal signal amplification. You are NOT making the camera more sensitive, you are simply turning up the volume. As anyone with any type of sound system will know, when you turn up the gain you get more hiss. This is because gain makes not only the desired signal bigger but also the noise. As a result adding gain or increasing the ISO is rarely a great thing to do.

So normally we want to use a digital camera at it’s native sensitivity wherever possible. The native sensitivity is where no gain is being added by the camera or 0dB. In ISO, well you need to find out what the native ISO is and be aware that different gamma curves will have different base ISO’s (which is why I prefer to use dB gain as 0dB = native sensitivity, least noise, best dynamic range, no matter what gamma curve).

To get the best possible image we then want to make our signal (picture information) as big as possible. As we can’t swap out the sensor, the only way to do that is to put as much light as possible onto the sensor. Obviously we don’t want to overload the sensor or exceed the limitations of the recording system, but generally the more light you get on the sensor, the better your pictures will be.

As the sensors noise output remains more or less constant, the best signal to noise ratio will be gained when you put a lot of light on the sensor. This generates a very large signal, so the signal becomes big compared to the noise and the noise becomes only a small percentage of the overall image.

If we are unable to get enough light onto the sensor to expose it fully then it is often tempting to add some gain to make the picture brighter. 6dB of gain is the equivalent to 1 stop of exposure. Just like f-stops, each time we go up a stop we are doubling. So adding 6db of gain doubles everything. It makes the picture the equivalent of one stop brighter, but it also doubles the noise. Adding 12dB gain multiplies the noise 4 times, adding 18dB multiplies the noise 8 times.

What if instead of adding gain to make the picture brighter we let 4x more light fall on the sensor (2 stops)? Well the image gets brighter by the equivalent of 2 stops but as we are not adding gain this means the desirable signal, the picture is now going to be the equivalent of 12dB bigger than the noise than it was before we added the 2 stops of light. That’s going to give you a much cleaner looking image.

How do you get more light onto the sensor? There are many ways such as using a faster lens with a larger aperture that will let more light through. Or you could try using a slower shutter speed (I often find it beneficial in low light to use a 1/24th or 1/25th shutter if there is not too much motion to cause the image to become excessively blurred). Then of course you can also add light to your scene by lighting it. It’s very rare to find noisy and grainy night scenes in feature films and that’s because the night scenes normally have well lit foregrounds but keep dark backgrounds to maintain the sensation of night time or darkness. High contrast is the key to good looking night scenes, well lit foregrounds or actors with deep, dark shadows and backgrounds.

The desire to have a good signal to noise ratio is one of the reasons why when shooting in log or raw you want to expose as brightly as you can (while still maintaining consistent exposure from shot to shot, scene to scene). It’s a little bit harder with standard gammas as we have things like the knee or highlight roll off to deal with. Plus the need to have a shot that looks correct straight out of the camera. But at the end of the day the best results are almost always gained when the gain is kept to a minimum (but don’t use negative gain as this can effect the dynamic range) and the amount of light falling on the sensor as high as possible.

In the next article I’ll give you an interesting experiment to try on a PMW-F5, F55 or PMW-FS7 that is very revealing  about the way ISO, gain, exposure and noise behaves that will show why exposing log or raw at +1 to +2 stops is so important.

What is “Exposure”?

This comes up in many of my workshops. It seems like a very simple question and the correct answer is really very simple, but many cameramen, especially those from a TV and video background actually get this a little wrong.

The word “expose” means to lay open, reveal or un-mask. In film terms it’s obvious what it means, it is opening the shutter and aperture/iris to let the correct amount of light fall on the film stock. In the video world it means exactly the same thing. It is how much light we allow to fall on the sensor.

Exposure is controlled by the speed of the shutter (how long we let the light in) and the aperture of the lens (the volume of light we let in).

So why do video people get a bit confused about exposure? Well it’s the down to the way we measure it with video cameras.

In the film world you would use a light meter to measure the intensity of the light in a scene and then perform a calculation to determine the correct amount of light we need to allow to fall on the film based on the sensitivity (ISO) of the film stock. But in the video world it is common practice to look at a monitor and asses the exposure by looking at, or measuring, how bright the picture is using a waveform meter, zebras or histogram etc.

What are we measuring when we look at a video picture or measure a video signal? We are not measuring how much light is falling on the sensor, we are measuring how bright the picture is on the screen or what the recording levels of the video signal are. Most of the time there is a direct relationship between on screen brightness and exposure, but it is important to make a clear distinction between the two as variations in brightness are not always due to changes in exposure.

It’s important because something like changing a cameras gamma curve will alter the brightness of the on screen image. This isn’t an exposure change, this is a change in the recording levels used by that particular gamma curve that in turn result in a change in the brightness levels you see on the screen. This is why if you take a camera such as the FS7 or F5/F55 and correctly expose the camera using Rec709 as the gamma curve you will find middle grey at 42% and white at 90%. Then switch to a Cinegamma or Hypergamma without adjusting the shutter speed or aperture and you will find middle grey at and white at much lower, perhaps the very same white target as low as 70%.

In both cases the exposure is correct, but the on screen brightness greatly different. The difference in on screen brightness comes from the different recording levels used by 709 and Hypergammas/Cinegammas. In order to be able to record a greater dynamic range than the 6 stops offered by 709, we need to compress the original 6 stop 709 range into a much smaller  range to make room for the extra  stops of dynamic range that the Hypergammas or Cinegammas can record.

So as you can see, exposure should really be the absolute measurement of the amount of light falling on the sensor. Brightness is related to exposure, but just how bright the picture should be depends on many factors of which exposure is just one. Once you realise that brightness and exposure are not always the same thing it becomes easier to understand how Cinegamma, Hypergamma, log and raw recording works. Levels are just levels and it doesn’t really matter whether something is recorded at 90%, 70% or 61%. Provided you have enough data (and this is where 10bit or better recording really helps) you have the same amount of picture information at both levels and you can easily shift from one level to the other without degrading the image in any way in post production.

Of course we do want to have our video levels in the finished production at the right levels to match the levels that the TV, monitor or display device is expecting. But when shooting, especially with non standard gammas such as Hypergamma or log it’s perfectly normal to have levels that are different to what we would see with plain vanilla 709 and these typically lower levels should not be considered too dark or under exposed, because they are not. Dark does not necessarily mean under exposed, nor does it mean a noisy image. How much noise there is depends on the signal to noise ratio which is dependant on the amount of light that we let on to the sensor. I’ll be explaining that in my next article.

PXW-FS7 firmware version 4.0 now available to download.

FS7-Firmware-V4 PXW-FS7 firmware version 4.0 now available to download.Sony have released firmware update version 4.0 for the PXW-FS7. This new firmware brings some welcome updates to the FS7 including the ability to move the focus magnification area away from the center of the screen.  Other new features include true 24p (as well as 23.98fps).

1. Support for Flexible Spot in Focus setting.
2. Support for XAVC-I 4K 24.00P.
3. Display for Video Signal Monitor is improved.
4. Operability of S&Q setting by assignable button is improved.
5. Remove Basic Authentication from items saved in all file.
6. Auto knee stability is improved.
7. Overall stability and operability of the camera is improved.
The firmware can be downloaded from here: https://www.sony.co.uk/pro/support/software/SET_BPE-SS-1238

Camera setup, reviews, tutorials and information for pro camcorder users from Alister Chapman.