In case you missed the webinars I presented yesterday here are recordings of the 2 afternoon sessions. The first one on HDR, what is it and what does it mean for you. The second is a question and answers session on Sony’s large sensor cameras, from the FS5 to the F55. There were quite a few a6300 and A7s questions thrown in there too!
Hopefully I will be able to find a sponsor that will be able to make these a regular event.
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.
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.
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%.
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.
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.
Well I didn’t know what “XDCAM Air” was so I had to ask. In a nutshell XDCAM Air is the name Sony are giving to the wireless and network functions of there more recent and forthcoming camcorders and it’s a cloud service especially for XDCAM.
So XDCAM Air covers things like proxy streaming from a camcorder, ftp uploading and the Sony QoS (quality of service) system that allows you to get great streaming image quality over less than ideal network conditions. Plus remote control of a camera or cameras over a wireless network.
But not only is XDCAM Air about existing capabilities, it is also about future possibilities with the introduction of remote NLE editing of content stored on a camera connected via the internet to the NLE. Other future possibilities are things like firmware updates and some engineering tasks over the Internet. As an example if your camera is playing up and engineer could be given remote access to the camera to look at any error codes or error logs stored in the camera. While the engineer might not be able to fix a hardware issue remotely it may mean that firmware bugs can be identified sooner or patches applied remotely. Perhaps one day I will be able to upload picture profiles or scene files directly to camera son the other side of the world.
After a brief teaser campaign Sony have now released details of a new raw recorder for the PMW-F5 and PMW-F55 cameras.
The AXS-R7 is a new more rugged dual slot recorder that works with A series AXS cards (that’s the newer smaller size, not the original large size cards). Being dual slot it should allow for relay recording.
The new recorder has a lot more processing power than the original to support new functions such as cache recording up to 30 seconds and has a more rugged housing with dust and moisture filters. One of the new features coming with this recorder is the ability to record at up to 120 fps in 4K raw. For this new faster AXS cards will be needed and these will be released at the same time as the recorder this summer.
To support the new recorder the F5/F55 cameras will get new firmware. Version 8 will also introduce the ability to record XAVC class 480 which in 4K is 480Mb/s at 24/25/30p and 960Mb/s at 50 and 60p.
So all in all a series of significant upgrades for these cameras that continue to just get better and better.
Here’s the full Sony press release:
Basingstoke – February 25th, 2016: Sony’s next generation of CineAlta products provides enhanced features for production professionals now shooting in 4K RAW with large sensor cameras; handling large files can be done easily while maintaining the highest levels of image quality.
The new products include an upcoming RAW recorder, the AXS-R7 for the F55/F5 and higher-speed AXS memory cards. These are complemented by the newest firmware (Version 8) for the F55 and F5, continuing Sony’s development and support of the CineAlta platform by adding new features and capabilities directly based on user feedback.
“These new technologies answer the question of ‘why shoot in 4K 16-bit RAW’? And, demonstrate Sony’s commitment to the F5 and F55’” said Ainara Porron, Marketing Manager, Cinematography, Sony Professional Solutions Europe. “Working in 4K RAW and High Dynamic Range (HDR) opens up new creative possibilities for production professionals who are not prepared to compromise on image quality.”
New RAW Recorder
Compared to previous Sony 4K recorders, the new recorder doubles 4K RAW recording from 60 FPS up to 120 FPS from the F55 camera. For shooting at higher frame rates, the recorder captures 2K RAW at up to 240 FPS from the F55 and F5, for playback with 10x super slow motion.
With the recorder, 4K shooters can take advantage of RAW cache recording at 23.98p for up to approximately 30 seconds while in standby mode, an important feature in documentary or wildlife production where capturing spontaneous action is required.
The new recorder is designed for rugged field performance. A metal filter separates and seals the recorder’s ventilation shaft from the electronics to prevent the entry of dust and water. The recorder’s camera connections are more secure, with a large top bracket that accepts four widely spaced 1/4-inch screws.
AXS Memory
The additions to the CineAlta line also include new high-performance versions of Sony’s AXS memory cards (1TB and 512 GB capacities) with sustained read and write speeds of 4.8 Gbps, and 44 minutes at 59.94p or 22 minutes at 120 FPS. The dual-slot recorder also accepts current A-series of AXS media, but the new cards are designed to support the write speeds required for 4K RAW 120 FPS recording for those who require that level of performance.
PMW-F55/F5 Firmware Version 8
The latest firmware update (Version 8) for the F55 and F5, upgrade license installed, enables support for XAVC 4K Class 480 recording at 23.98p, 24p, 25p and 29.97p. Leading third-party vendors already support XAVC 4K Class 480, for those creative professional requiring a higher data rate version of XAVC.
“These newest additions and updates to our CineAlta platform are all the direct result of user feedback,” Porron added. “It’s no longer about simply delivering a product. It’s about delivering the right products that can grow with a customer and fit within a workflow that is constantly evolving as production requirements change.”
For a full list of features and capabilities, visit pro.sony.eu/cinematography
Planned availability is as below:
[if !supportLists]· [endif]AXS-R7 New RAW recorder: Summer 2016
[if !supportLists]· [endif]AXS-A1TS48 Media (1TB): Summer 2016
[if !supportLists]· [endif]AXS-A512S48 Media (512 GB): Summer 2016
[if !supportLists]· [endif]Firmware version 8: Summer 2016
More details will be announced at NAB.
Has anyone else noticed that Adobe now include XAVC Class 480 in the codec options for exporting XAVC from Adobe Premiere via Media Encoder?
In case you don’t know what it is, class 480 is the 480Mb/s version of 4K XAVC. This gives a bit rate of…… drum roll……. 480Mb/s at 24/25/30fps. At 50 and 60fps it runs at a whopping 960Mb/s, this is the top limit for XAVC in it’s current form.
Sony’s PMW-F5/F55 and the FS7 currently record XAVC using Class 300 which is up to 300Mb/s at 24/25/30fps or 600Mb/s at 50/60p. So as you can see Class 480 has the potential to improve the compressed image quality from these cameras still further should it ever make it into a camera. Looking at what the cameras can currently do I’m not sure that this is possible with existing SxS or XQD media. 960Mb/s is the same data rate as Sonys 16 bit 24fps raw and it’s not possible to record that to SxS cards.
Coming back to Premier: Some interesting things happen in Premiere if you try to export an XAVC originated project out using Class 480. If the clips in your timeline are not adjusted in any way, in other words; exactly as shot, then if you export and choose Class 480 nothing happens to the footage. Premiere will “smart” export them exactly as they are as Class 300. This means that there will be absolutely no loss of image quality as the clip is not re-compressed. However if the original clip has been adjusted, for example graded, re-sized, a caption added etc then the clip will be encoded at 480Mb/s. From what I can tell where you have a mix of treated and untreated clips in a project Premiere is smart enough to pass through the untreated clips while bumping up any treated clips to 480.
Class 480 is seen as a mastering format by Sony. The extra data and lower compression makes it particularly suited to HDR productions.
More good news for Sony PMW-F55 owners. A rather obscure announcement over on the official Sony user group states that the PMW-F55 will gain the ability to record 4K raw at up to 120fps via an optional future accessory.
This is great news for F55 owners. We can hope that perhaps this option will get extended to the F5 as well (after all the FS700 and can do it for short bursts and possibly the FS5 will be able to do it too using their internal memory caches to cache 4 seconds of the 4K HFR before copying it to the R5 or Odyssey). I do hope that the F55 4K raw isn’t limited to a 4 second burst and that it’s the full 16 bit raw that you get at up to 60fps.
Quite what the optional accessory will be I don’t know, but my guess would be a new raw recorder or new faster AXS media, but it could also be an internal upgrade allow the high speed raw to be passed to the existing R5 and AXS media.