Tag Archives: exposure

cinematography, FX3, FX30, FX6

Do I Need To Always Overexpose S-Log3?

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This is another one from Social Media and it the same question gets asked a lot. The short answer is…………

NO.

Even with Sony’s earlier S-Log3 cameras you didn’t need to ALWAYS over expose. When shooting a very bright well lit scene you could get great results without shooting extra bright. But the previous generations of Sony cameras (FS5/FS7/F5/F55 etc) were much more noisy than the current cameras. So, to get a reasonably noise free image it was normal to expose a bit brighter than the base Sony recommendation, my own preference was to shoot between 1 and 1.5 stops brighter than the Sony recommended levels (click here for the F5/F55, here for the FS7 and here for the FS5).

The latest cameras (FX30, FX3, FX6, FX9 etc) are not nearly as noisy, so for most shots you don’t need to expose extra bright, just expose well (by this I mean exposing correctly for the scene being shot). This doesn’t mean you can’t or shouldn’t expose brighter or darker if you understand how to use a brighter/darker exposure to shift your overall range up and down, perhaps exposing brighter when you want more shadow information and les noise at the expense of some highlight range or exposing darker when you must have more highlight information but can live with a bit more noise and less shadow range.

What I would say is that exposure consistency is very important. If you constantly expose to the right so every shot is near to clipping then your exposure becomes driven by the highlights in the shot rather than the all important mid range where faces, skin tones, plants and foliage etc live. As the gap between highlights and the mids varies greatly exposure based on highlights tends to result in footage where the mid range is up and down and all over the place from shot to shot and this makes grading more challenging as every shot needs a unique grade. Base the exposure on the mid range and shot to shot you will be more consistent and grading will be easier.

This is where the CineEI function really comes into its own as by choosing the most appropriate EI for the type of scene you are shooting and the level of noise you are comfortable with and basing the exposure off the image via the built in LUT will help with consistency (you could even use a light meter set to the ISO that matches the EI setting). Lower EI for scenes where you need more shadow range or less noise, higher EI for scenes where you must have a greater highlight range. And there is no -“One Fits All” setting, it depends on what you are shooting. This is the real skill, using the most appropriate exposure for the scene you are shooting (see here for CineEI with the FX6 and with the FX9)

So how do you get that skill? Experiment for yourself. No one was born knowing exactly how to expose Log, it is a skill learnt through practice and experimentation, making mistakes and learning from them. In addition different people and different clients will be happy with different noise levels. There is no right or wrong amount of noise. Footage with no noise often looks very sterile and lifeless, but that might be what is needed for a corporate shoot. A small to medium amount of noise can look great if you want a more film like look. A large amount of noise might give a grungy look for a music video. Grading also plays a part here as how much contrast you push into the grade alters the way the noise looks and how pleasing or objectionable it might be.

All anyone on here can do is provide some guidance, but really you need to determine what works for you, so go out and shoot at different EI’s or ISO’s, different brightness levels, slate each shot so you know what you did. Then grade it, look at it on a decent sized monitor and pick the exposure that works for you and the kinds of things you shoot – but then also remember different scenes may need a different approach.

FX3, FX30

What do the FX3 and FX30 zebras measure when using the Cine EI modes?

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This is a question that keeps popping up:

What do the zebras measure when shooting S-Log3 using the CineEI modes in the FX3 and FX30?

The convention for zebras with the majority of cameras is that zebras are a viewfinder applied measurement. As such they almost always measure the “viewfinder” image. As the LCD on the FX series cameras is in effect the viewfinder, the zebras measure what you see on that screen. So, when you have a LUT on, the zebras measure the LUT, not the S-Log3.

Common ways to use the zebras include measuring skin tones, which for the default s709 LUT will be somewhere in the region of 60% depending on the face brightness. You could also use the LUT’s to measure the brightness of a white card or white piece of paper which should be around around 81% for a proper white card or 83% for white paper.  

You could also use Zebras to indicate when you are close to clipping Depending on the LUT that you are using the peak LUT output will typically be at 100%, so a common usage would be to have Zebra 2 (which measures from the zebra point and everything above) set to a touch below 100 to act as a clipping indicator. BUT it must also be remembered that depending on the Exposure Index in most cases the LUT will have a lower highlight range than the S-Log3 recordings. So, when your highlights hit 100% on the LUT there may still be available headroom in the S-Log3 recordings. If you end up backing off your exposure every time the LUT clips you may be missing out on the full recording range and un-necessarily bringing the mids and shadows down. So, my preference is to measure the exposure of a white card or skin tones and to get the mid range and shadows right, rather than obsessing over small amounts clipping.

The s709 LUT does fit the full highlight range of the S-Log3 into it’s output. But as there is only a tiny difference between +5 and +6 stops (approx 1.5%) it is very difficult to determine what is clipped and what is 1 stop below clipping. +4 stops above middle grey is output at 93% and +6 above middle grey is at 98% so it becomes very difficult to see what is really going on in the highlights via the LUT when the top 2 stops are crammed into just 5% of the recording range. Zebra 2 set to 95% (for example) would appear over 1.5 stops below clipping, even if set to 97% zebras will show almost a full stop below clip.

It is one of the frustrations of the FX3/FX30 that there is no way to monitor via the LUT and measure the S-Log3 at the same time.

FX3, FX30, FX6, PXW-FX9, Venice

You Don’t Always Need To Over Expose S-Log3!

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For some reason many people now believe that the only way you can shoot with S-Log3 is by “over exposing” and very often by as much as almost 2 stops (1.7 stops is often quoted).

When Sony introduced the original A7S, the FS5, F5, F55 and FS7 shooting S-Log3 with these cameras was a little tricky because the sensors were quite noisy when used at the relatively high base ISO’s of these cameras. When exposed according to Sony’s recommendation of 41% for middle grey and 61% for a white card the end result would be fairly noisy unless you added a good amount of post production noise reduction. As a result of this I typically recommended exposing these particular cameras between 1 and 2 stops brighter than the base level. If using the F5 or FS7 I would normally use 800EI which would lead to an exposure +1.3 stops brighter than base. This worked well with these cameras to help control the noise, but did mean a 1.3 stop loss of highlight range. In other examples I used to recommend exposing a white card at white at 70% which would equate to an exposure a touch over 1 stop brighter than the base level.

With the introduction of the original Venice camera and then the FX9 we got a new generation of much lower noise sensors with dual base ISO’s. It soon became clear to me that these new cameras didn’t  normally need to be exposed more brightly than the Sony recommended levels when using their low base ISO’s and even at their high base ISO’s you can typically get perfectly acceptable results without shooting brighter, although sometimes a small amount of over exposure or a touch of noise reduction in pots might be beneficial. No longer needing to expose more brightly brought with it a useful increase in the usable highlight range, something the earlier cameras could struggle with.

Then the A7S3, FX6 and FX3 came along and again at the lower of their base ISO’s I don’t feel it is necessary to shoot extra bright. However at the 12,800 high base ISO there is a fair bit more noise. So I will typically shoot between 1 and 2 stops brighter at the high base ISO to help deal with the extra noise. On the FX6 and FX3 this normally means using between 6400 and 3200 EI depending on the scene being shot.

Even though I and many others no longer advocate the use of extra bright exposures at the lower base ISO’s with these newer cameras it really does surprise me how many people believe it is still necessary to shoot up to 2 stops over. It’s really important to understand that shooting S-Log3 up to 2 stops over isn’t normal. It was just a way to get around the noise in the previous cameras and in most cases it is not necessary with the newer cameras. 

Not having to shoot brighter means that you can now use the Viewfinder Display Gamma Assist function in the A7S3, A1 or the FX9 (for those times you can’t use a LUT) to judge your exposure with confidence that if it looks right, it most likely will be right. It also means that there is no longer any need to worry about offset LUT’s or trying to correct exposure in post before applying a LUT.

Of course, you can still expose brighter if you wish. Exposing brighter may still be beneficial in scenes with very large shadow areas or if you will be doing a lot of effects work. Or perhaps simply want an ultra low noise end result. But you shouldn’t be terrified of image noise. A little bit of noise is after all perfectly normal.

And one last thing: I don’t like the use of the term “over exposing” to describe shooting a bit brighter to help eliminate noise. If you have deliberately chosen to use a low EI value to obtain a brighter exposure or have decided to expose 1 stop brighter because you feel this will get you the end result you desire this is not (in my opinion) “over exposure”. Over exposure generally means an exposure that is too bright, perhaps a mistake. But when you deliberately shoot a bit brighter because this gets you to where you want to be this isn’t a mistake and it isn’t excessive, it is in fact the correct exposure choice.

cinematography, Shooting Tips

Zebras and Log – Use a narrower window/range.

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If you are using Zebras to measure the exposure of a log gamma curve you should consider using a narrower Zebra window.

Why?

From middle grey to white (50% to 90%) in the world of standard dynamic range Rec-709 each stop occupies approximately 16% of the recording range. Typically the default zebra window or zebra range used by most cameras is 10% (often +/- 5%). So, when Zebras are set to 70% they will appear at 65% and go away at 75%. For Rec-709 and most conventional SDR gammas this window or range is around 3/4 of a stop, so less than 1 full stop and generally reasonably accurate.

But if using most Cineon based log curves, such as Sony’s S-Log3, between middle grey and white (41% to 61%) each stop only occupies around 8% of the recording range, half the range used by Rec-709. As a result if you use a default 10% zebra window, zebras will appear over a 1.2 stop range, this is excessive and introduces a large margin of exposure error. Compared to Rec-709 the zebras will only be half as precise, especially if you are trying to measure the brightness of a grey card or white card.


I recommend reducing the width of the Zebra window to 6% when using Zebras to measure skin tones within the S-Log3 image (if measuring a Rec-709 LUT there is no need to change the window). This will then give a similar range and accuracy to a 10% window in 709. If you are using zebras to measure a white card or grey card then consider bringing the zebra window down to 2%  to gain a more accurate reading of the white/grey card.

fx-cameras-zebras_4.32.1-scaled Zebras and Log - Use a narrower window/range.
FX6(left) and FX3 (right) zebras set to measure S-Log3 white card exposure.


The zebra window or range can normally adjusted in the cameras menu under the zebra settings. On the Sony Alpha’s and and FX3/FX30 you can adjust the range of the C1 and C2 custom zebras.

Everything Else

FX6 Guide To Cine EI Updated

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CineEI-diagram-1-scaled FX6 Guide To Cine EI UpdatedI have updated my guide to the FX6’s CineEI mode to ensure it is up to date and compatible with any changes introduced in the Version 3 firmware update. The revised and updated guide includes new graphics that I hope will make the CineEI mode easier to understand for those completely new to shooting S-Log3 and the Sony FX6.  

If you are struggling to get to grips with CineEI in the guide I take a step by step approach to using S-Log3 on it’s own without any LUT’s or EI offsets, then introducing the s709 LUT at the base EI and then show how you use different EI levels to offset you exposure. There are suggested exposure levels for both white and grey cards as well as skin tones.

Click here to go to my updated FX6 CineEI guide.

FX3, FX30, FX6, PXW-FX9, Shooting Tips

Low Light Shooting – S-Log3 or S-Cinetone?

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A fundamental aspect of electronic cameras is that the bulk of the noise comes from the sensor. So the amount of noise in the final image is mostly a function of the amount of light you put on to the sensor v the noise the sensor produces (which is more or less constant). This is known as the signal to noise ratio, often abbreviated to SNR.

Whether you use S-Log3 or S-Cinetone, even though the base ISO number the camera displays changes the sensitivity of the camera is actually the same, after all we are not changing the sensor when we change modes. In fact if you set the camera to dB you will see that in custom mode the base for both S-Cinetone and S-log3 (and every other gamma curve) is always 0dB.

All we are changing when we switch between S-Cinetone and S-Log3 is the gamma curve – which is a form of gain curve. The base ISO number changes between S-Log3 and S-Cinetone because if you were using an external light meter this would be the number to put into the meter to get the “correct” exposure, but the actual sensitivity of the camera remains the same.

First let’s think about what is happening at the base ISO of each if we were to use an external light meter to set the exposure…..

If we shoot at S-Cinetone and use the 320 ISO value in the light meter the aperture will be a little over a stop more open than if you shoot with S-Log3 and use 800 ISO for the light meter. So when using S-Cinetone at the base ISO there is a little over twice as much light going on to the sensor compared to S-Log3 at the base ISO and as a result the S-Cinetone will be much less noisy than the S-Log3. Not because of a sensitivity or noise performance difference but simply because you are exposing the sensor more brightly.

And if we use the SAME ISO value for S-Cinetone and S-Log3?

So now think about what might happen if you were to put 400 ISO into your light meter and use the values for shutter and aperture the meter gives and shoot with either S-Cinetone or S-Log3 using the very same aperture and shutter settings so that the same amount of light is hitting the sensor for both. The result will be that the amount of noise in the resulting image will be broadly similar for both and the same would happen if you were to use, let’s say, 4000 ISO (assuming you switch to high base for both).

There will tend to be a bit more noise in the S-Log and CineEI at the default settings, because by default NR is turned off in CineEI. But with the same in camera NR settings, again both the S-Log3 and S-Cinetone will have very, very similar noise levels when the sensor receives the same amount of light.

What about when there isn’t enough light?

So – when you are struggling for light, both will perform similarly from a noise point of view. BUT where there may be a difference is that with S-Cinetone all your image processing is done before it is compressed by the codec and what you see in the viewfinder is what you get. With S-Log3 the “underexposed” image gets compressed and then you will need to process that in post and when you add your post corrections this will be to the recorded image + compression artefacts so there will always be a lot of uncertainty as to how the final image will come out.

Personally I tend to favour S-Cinetone for under exposed situations. Generally if it’s under exposed dynamic range isn’t going to be an issue. S-Cinetone also spreads what image information you do have over a greater range of code values than S-Log3 and this may also help a little. But there is no right or wrong way and any differences will be small.

FX6, PXW-FS7, PXW-FX9

Using Auto Exposure With Cine EI.

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First – What is “Exposure”

Something I find useful to consider is that “Exposure” is the amount of light that you put onto the sensor or film stock in your camera. It isn’t brightness, it is how much light. If you think about it, if you use a light meter to find you exposure settings, the light meter has no idea how bright the pictures will be, all it does is give you the shutter and aperture values needed to put the correct amount of light onto the sensor or film stock.

How Cine EI Works.

Next we need to think about how Cine EI works. You have to remember that when shooting using Cine EI the only thing that changes when you change the EI value is the brightness of the LUT and it is also worth considering that different LUTs may be completely different brightness. There is no change to the sensitivity of the sensor and no direct change to the brightness of what is recorded. To change the brightness of what is recorded YOU must change the aperture, shutter speed or ND etc. Normally you would monitor your images via a LUT and then you must adjust the exposure so the image on the viewfinder looks correct at the new Exposure Index, or use the waveform to measure the LUT and use this to set the exposure for the new EI. And by changing the exposure you are adding an exposure offset putting more (or less) light on to the sensor than would be normal at the base EI.

AE In Cine EI.

If you wish to use auto exposure in the Cine EI mode then you need to understand that the camera’s auto exposure system measures what is being recorded. It does not measure the LUT levels. The auto exposure system is unaware of your desire to expose the sensor more or less brightly than normal and will always base the exposure on the base ISO, not the Exposure Index. As a result if you are using AE and you go from 800 EI to 400 EI the image seen via the internal LUT will get darker by one stop, the AE will NOT compensate for the lower EI.  If you were to manually brighten the exposure by one stop the cameras exposure meter will think you are now over exposed – because you are!


Adding Offsets.

The only way around this is to add an offset to the AE system to account for the offset added by the different Exposure Index. For example if you want to shoot at 400EI (The LUT becoming 1 stop DARKER) then you would need to add a +1.0 stop offset to the cameras AE settings to offset the exposure 1 stop brighter. Each time you halve the EI you should add an extra +1 stop of offset. Each time you double the EI you should include an extra -1 stop offset.

There are a couple of ways to do this but the quickest is to use the Quick Menu function that is by default assigned to button 5 on the hand grip or button 8 on the handle. Press the direct menu button and then use the thumbstick to go the AE+0 indication just above the shutter speed indicator and add your offset.

Or you can long press the menu button to go into the cameras main menu then go to the – Shooting – Auto Exposure page and add your offset to the Level setting.

I don’t recommend the use of Auto Exposure in Cine EI. For a start AE uses the average brightness of the scene to set the exposure level, often this isn’t appropriate for Log. When shooting with log generally you want to ensure that it is your mid range is exposed at the right level and you don’t want bright highlights to result in an under exposed mid range. Additionally if the exposure changes mid shot this can make grading very difficult. If you do use auto exposure in Cine EI, then as well as adding any necessary offsets I also recommend slowing down the responsiveness of the AE using the “Speed” setting in the Auto Exposure menu. Using a value such as -60 will slow down the rate at which the AE will change the exposure which helps avoid rapid auto exposure changes for momentary light changes within the scene.

It is really important to remember that Exposure is NOT brightness. Exposure is how much light you put on the sensor. A light meter doesn’t know how bright you want your pictures to be. All it knows is the correct amount of light to put on to the sensor for the “correct” exposure. If using an external light meter provided you put the right values into your light meter it will give you the correct exposure settings, even though it has no idea how bright your pictures will be and the camera’s internal exposure meter acts in a similar way, so offsets are needed to match each EI you use.

300x250-ad-box1 Using Auto Exposure With Cine EI.
PXW-FS5

Shooting Raw With The FS5 And Ninja V+

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This came up in one of the user groups today and I thought I would repeat the information here.

One issue when using the Atomos Ninja V+ rather than an older Atomos Shogun or Inferno is that the Ninja V+ doesn’t have an internal S-Log2 option. This seems to cause some users a bit of confusion as most are aware that for the best results the FS5 MUST to be set to PP7 and S-Log2 as this is the only setting that fully optimises the sensor setup.
 
When you shoot raw, you are recording linear raw, the recordings don’t actually have any gamma as such and they are not S-log2 or S-Log3, they are raw. The S-Log2 setting in the FS5 just ensures the camera is optimised correctly. If you use the S-Log3 settings, what you record is exactly the same – linear raw, just with more noise because the camera isn’t as well optimised.
 
Any monitor or post production S-Log2 or S-Log3 settings are simply selecting the intermediate gamma that the raw will be converted to for convenience. So when the Ninja V+ states S-Log3 this is simply what the Ninja converts the raw to, before applying any LUT’s. It doesn’t matter that this is not S-Log2 because you didn’t record S-Log2, you recorded linear raw. This is simply what the Ninja V+ will use internally when processing the raw.
 
You have to convert the raw to some sort of gamma so that you can add LUT’s to it and as S-Log3 LUT’s are commonly available S-Log3 is a reasonable choice. With earlier recorders you had the option to choose S-Log2 so that when viewing the native S-Log2 output from the camera, what you saw on the monitors screen looked similar to what you saw on the FS5’s LCD screen when the FS5 was set to S-Log2. But S-Log2 is no longer included in the latest monitors, so now you only have the option to use S-Log3. But from an image quality point of view this monitor setting makes no difference and has no effect on what is recorded (the FS5 should still be set to PP7 and S-Log2).
 
In post production in the past, for consistency it would have been normal to decode the raw to S-Log2 so that everything match throughout your production pipeline from camera to post. But again, it doesn’t really matter if you now decode the raw to S-Log3 instead if you wish. There will be no significant quality difference and there is a wider range of S-Log3 LUT’s to choose from.
 
If the footage is too noisy then it is under exposed, it’s the only reason why the footage will be excessively noisy. It is true that raw bypasses the majority of the cameras internal noise reduction processes, but this only makes a small difference to the overall noise levels. 

Even with the latest Ninja V+ what is recorded when outputting raw from the FS5 is 12 bit linear raw.
 
12 bit Linear raw is a somewhat restricted format. 12 bits is not a lot of code values to record a high dynamic range linear signal. This is why most cameras use log recording for wide dynamic ranges, log is much more efficient and distributes the available recording data in a way very sympathetic to the way human vision works.
 
In practice what this means is that the 12 bit linear raw has LOTS of data and image information in the upper mid range and the very brightest  highlights. But relatively very little picture information in the lower mid range and shadows. So if it is even the slightest bit under exposed the image will degrade very quickly as for each stop yu go down in brightness you halve the amount of image information you have.
 
In an underexposed image the noise will be very coarse in appearance and the image will be difficult to grade. You really do need to expose the raw nice and bright and because of the way the data is distributed, the brighter you can get away with the better. Never be afraid of exposing linear raw “just a little bit brighter”. It is unlikely to severely bite you if you are over exposed but highly likely to bite you if it is even a fraction under.
 
The 12 bit linear raw from the FS5 is not going to be good in low light or when shooting scenes with large shadow areas unless you can expose bright so that you are bring your levels down in post. If you have to bring any levels up in post the image will not be good.
 
Raw is not a magic bullet that makes everything look great. Just as with S-Log it must be exposed carefully and 12 bit linear raw is particularly unforgiving – but when exposed well it is much better than the internal 8 bit log recordings of the FS5 and can be a fantastic format to work with, especially given the low cost of an FS5.
 
I recommend going back to basics and using a white card to measure the exposure. If monitoring the raw via S-Log3 the white card needs to be exposed around 70%. If using a light meter with the FS5 set the light meter to 640 ISO.
 
If you do want to use a LUT on the Ninja to judge your exposure use a LUT with a -1.5 stop offset. The darker LUT will encourage you to expose the raw brighter and you will find the footage much easier to grade. But it should also be considered that it is also quite normal to add a small amount of selective noise reduction in post production when shooting raw. 
cinematography, Shooting Tips, Technology

My Exposure Looks Different On My LCD Compared To My Monitor!

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This is a common problem and something people often complain about. It may be that the LCD screen of their camera and the brightness of the  image on their monitor don’t ever seem to quite match. Or after the shoot and once in the grading suite the pictures look brighter or darker than they did at the time of shooting.

A little bit of background info: Most of the small LCD screens used on video cameras are SDR Rec-709 devices. If you were to calibrate the screen correctly the brightness of white on the screen would be 100 Nits. It’s also important to note that this level is the level that is also used for monitors that are designed to be viewed in dimly lit rooms such as edit or grading suites as well as TV’s at home.

The issue with uncovered LCD screens and monitors is your perception of brightness changes according to the ambient viewing light levels. Indoors in a dark room the image on it will appear to be quite bright. Outside on a Sunny day it will appear to be much darker. It’s why all high end viewfinders have enclosed eyepieces, not just to help you focus on a small screen but also because that way you are always viewing the screen under the very same always dark viewing conditions. It’s why a video village on a film set will be in a dark tent. This allows you to then calibrate the viewfinder with white at the correct 100 NIT level and then when viewed in a dark environment your images will look correct.

If you are trying to use an unshaded LCD screen on a bright sunny day you may find you end up over exposing as you compensate for the brighter viewing conditions. Or if you also have an extra monitor that is either brighter or darker you may become confused as to which is the right one to base your exposure assessments on. Pick the wrong one and your exposure may be off.  My recommendation is to get a loupe for the LCD, then your exposure assessment will be much more consistent as you will then always be viewing the screen under the same near ideal conditions.

It’s also been suggested that perhaps the camera and monitor manufacturers should make more small, properly calibrated monitors. But I think a lot of people would be very disappointed with a proper calibrated but uncovered display where white would be 100 NITs as it would be too dim for most outside shoots. Great indoors in a dim room such as an edit or grading suite but unusably dim outside on a sunny day. Most smaller camera monitors are uncalibrated and place white 3 or 4 times brighter at 300 NIT’s or so to make them more easily viewable outside. But because there is no standard for this there can be great variation between different monitors making it hard to understand which one to trust depending on the ambient light levels.

FX3, FX6, PXW-FX9, Shooting Tips

Chroma Key and S-Cinetone

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A question poped up today asking about how to expose S-Cinetone when shooting green screen. 
The answer is really quite simple – no differently to how you would expose S-Cinetone anywhere else. But, having said that it is important to understand that S-Cinetone is a bit different to normal Rec-709 and this needs to be considered when shooting for chroma key or green screen.

S-Cinetone’s highlight roll off and shoulder starts much lower than most “normal” rec-709 curves. From around 73% the gamma curve changes and starts to compress the levels and reduce contrast. In the shdows there is a variable toe that increases contrast at lower brightness levels. The nominal “normal” brightness levels are also lower, all part of the contemporary film like look S-Cinetone is designed to give. A 90% reflectivity reference white card would be exposed at approx 83% instead of the more normal 90% (if you were using a light meter you should end up with a 90% white card at 83IRE). A white piece of paper will be a bit brighter than this as printer and copier paper etc is designed to look as bright as possible, typically printer paper comes out around 3 to 5% brighter than a proper white card.

The lower start to the highlight roll-off means that if you place skintones around 70% the brighter parts of a face will be affected by the rolloff and this will make them flatter. Expose skin tones at 60% and the face will be more contrasty and in my opinion look better. Although darker this would still be well with the “normal” exposure range for S-Cinetone so you will not have excessive noise and it will still key well.

exposing-cinetone-600x316 Chroma Key and S-Cinetone

S-Cinetone would be considered correctly exposed when a 90% white card is exposed between 78% and 88%. This is quite a wide window and is due to the way S-Cinetone is designed to give differening contrast levels simply by exposing a touch brighter or darker. The variable toe and shoulder mean that exposing brighter will make the image flatter and exposing darker more contrasty. Exposing as you would with normal Rec-709 levels with a white card at 90% will place skintones rather higher than “normal” and they will appear very flat. So either expose so a white card falls in the 78-88% window or use a calibrated monitor to observe how the skin tone look and be careful not to overexpose them.

Your greenscreen should be between 40IRE and 60IRE for a good clean key, I normally aim for 50IRE with S-Cinetone, but provided you don’t go below 40IRE or above 60IRE you should be good.