I 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.
I’ve been getting a lot of questions about the new FX3 firmware update. So, I thought I would put my answers to the questions here in one place. But before I get to my notes on what the firmware does, I will just say that if you are a Mac user, I recommend trying to borrow a PC to do the update. It is much much easier to do the update with a PC than a Mac! The firmware update is well worth doing. At first it might appear that the update makes it impossible to do some things the camera did before, but, if you follow my notes you will see that this is not actually the case.
What is the base ISO for S-Log3 in version 2? In the CineEI and CineEI Quick modes the base ISO defaults to 800/12800 ISO. This is different to before, but brings the FX3 in line with the other Sony Cinema line cameras and most other current digital cinema cameras. When not using the dedicated CineEI modes the base ISO for S-Log3 seems to revert back to 640 ISO as indicated by the way the camera adds a pair of bars, above and below the ISO indication from 500 ISO and down, to warn that you are below the native ISO.
Help, I can’t output 4K/UHD and record 4K/UHD internally while using the CineEI modes! It takes a lot of extra processing power to apply the LUT’s to the preview image while recording S-Log3. Unfortunately this seems to mean that there is no longer enough processing power to both record internal 4k/UHD and output 4K/UHD and have LUT’s at the same time. You can record internal 4K and 4K output raw, that’s one option. And you can record 4K and output HD. But if you need to record 4K/UHD internally and output 4K/UHD S-log3 you will need to come out of the cameras log mode.
How do you shoot S-Log3 when not using the Log modes? When you are not using the Log modes you will find that the old S-Log3 and S-Log2 picture profiles (7,8 and 9) are missing. However you can still go into any of the other picture profiles and change the gamma to S-Log3 and the color mode to S-Gamut3.cine or S-Gamut3. S-Log2 has been removed and is no longer available, but as S-Log2 is incapable of recording the full dynamic range of the FX3 this isn’t a big deal. Shooting S-Log3 this way allows you to record 4K/UHD internally and output 4K/UHD over the HDMI as in the previous version 1 firmware. I suspect that PP7/8/9 were removed simply to encourage users to use the dedicated log modes where everything is fully optimised for log rather than using a picture profile where any ISO can be used or other settings changed that may degrade the log.
What does “Embed LUT LUT File” do? When Embed LUT File is enabled the camera stores the LUT used in the “Private”, “M4ROOT”, “General” metadata folder on the recording card. In addition metadata about the LUT and the chosen exposure index is saved in the clip file. The LUT is NOT BAKED IN to the file, the recording remains as S-Log3. When you import the clip into the latest version of Sony’s Catalyst Browse software the LUT you used when shooting is automatically applied to the clip as well as the correct exposure offset for the Exposure Index used. The end result is the clip looks exactly the same in Catalyst Browse as it did on the cameras LCD when you were shooting. But because it is still an S-Log3 recording, you can still manipulate it as much as before and if you want you could use a different LUT in post. Hopefully in the future other edit and grading software will also read this metadata and apply the LUT automatically, this is really how this should all work (hope the FX6/FX9 get the same functionality).
How do I load a custom LUT into the FX3 camera? Start with an empty SD card and format the card in the camera. This will create the necessary folders needed for the LUT on the card. The FX3 accepts 33x 3D cube LUTS, this is the most commonly found LUT format. Next copy your chosen LUT to the “PRIVATE”, “SONY”, “PRO”, “LUT” folder. Then put the card into the camera and go to the menu “Exposure/Color”, “Color/Tone”, “Manage User LUTs” option. From here you will first chose a User memory slot to load the LUT into. You will then be prompted to choose the SD card that you saved the LUTs to, and then LUT you wish to load from the card. The LUT will be saved to the slot chosen – the original LUT name is kept, but if the name is too long it will be abbreviated. Once the LUT has been loaded into the camera you can then select it from the new Home Menu – page 1. You can save up to 16 user LUTs.
How do I bake in a LUT? To bake in a LUT you have to come out of the cameras dedicated Log shooting mode. In the normal shooting mode if you go to the menu’s “Exposure/Color”, “Color/Tone”, “Picture Profile” page you will see that as well as the picture profiles, a little lower down you will find 4 “PPLUT” settings. These initially correspond to the first 4 user LUT memories and allow you to select those LUTs as a baked in look. But if you have saved more than 4 user LUTs do not despair. You can go into the “PPLUT” setting and if you select “Basic Look” you can select any of your saved user LUTs.
What do the Zebras or histogram measure in the CineEI mode? The Histogram and zebras measure the brightness of the LUT when using the CineEI mode. Do note that when correctly exposed the s709 LUT will be a touch darker than S-Cinetone or normal Rec-709.
Average Skin Tones
90% Reflectivity white card (add 2-3% for white paper).
Will the A7S3 get the same firmware? As far as I know, no it will not. It is my understanding that this firmware is specifically for the FX3 as the FX3 is sold as a part of the Cinema Line and primarily as a video camera. The A7S3 is not part of the cinema line and is sold primarily as a photo camera that also shoots great video.
The FX6’s CineEI mode is designed to make shooting using S-Log3 or raw easy and straightforward. It optimises the camera so that settings such as the recording ISO, noise reduction and sharpening are all optimised for recording the highest possible quality S-Log3 or raw material with the largest possible dynamic range.
It makes sure that the S-Log3 or raw recordings are optimised for grading. In addition you can use a LUT (Look Up Table) in the viewfinder or on the HDMI/SDI output to provide a close approximation of how your footage will look after it’s been graded and this LUT will also to assist you in getting the exposure exactly right.
HINT: What is a LUT? A LUT is a simple Look Up Table of input values that represent different levels in the recording format (in this case S-Log3) and then converts those input values to new output values that are appropriate for the monitor or display range you are using. This conversion can included stylised adjustments to give the output image a specific look. A LUT can be applied to S-Log3 material to convert it so that it looks correct on a normal viewfinder or monitor.
To use the Cine EI mode correctly you must monitor what you are shooting via a LUT. Once you have a LUT enabled and you are viewing the LUT, either in the viewfinder or on a monitor an exposure offset can be applied to the LUT to make it darker or brighter than normal. This LUT brightness offset is used to allow you to deliberately offset how bright the recordings are, this is the “EI” or Exposure Index part of CineEI. More on that later.
BUILT IN LUTS
The FX6 has 3 built in LUTs, s709, 709(800) and S-Log3. In addition to the built in LUTs you can load your own “user MLUTs” into the camera as what the FX6 calls “Base Looks”. This makes this a very flexible and capable system. Sony refer to LUTs in the FX6 as MLUT’s or Monitor Look Up Tables. MLUTs = LUT’s they are not different.
Loading Your Own LUTs.
If you want to load you own LUTs into the camera these must be 3D Cube LUT’s and should be placed in the
— Private : SONY : PRO : LUT —
folder of an SD card or CFExpress card that has been formatted in card slot 2 of the FX6 (the lower slot). The LUT should be 17x or preferably 33x cube LUT designed for use with S-Log3 and SGamut3.cine. They are loaded via the main menu PAINT – BASE LOOK page.
As your material will require grading in post production, if you are shooting UHD or 4K you should NOT use XAVC-L because in UHD/4K XAVC-L is 8 bit 4:2:0. A much better choice is XAVC-I which is always 10 bit 4:2:2 and/or raw.
FIXED RECORDING ISO.
Once the camera is set to use the CineEI mode the recording sensitivity is fixed to either 800 ISO when in Lo Base sensitivity or 12,800 ISO when the camera is set to Hi Base sensitivity. These values cannot be changed and your recordings will always take place at one of these sensitivity levels.
Note: ISO and EI are not the same thing, even though they use similar numbers. ISO is very specifically the sensitivity of the camera, it is a measure of the sensors response to light. EI (Exposure Index) is a camera setting that alters the cameras EXPOSURE settings, EI does not change the sensitivity of the camera in any way.
ENABLE A MLUT (LUT).
To take full advantage of the Cine EI mode the next step is to enable a MLUT for the viewfinder and also optionally for the HDMI and SDI outputs. YOU MUST ENABLE A MLUT FOR CINE EI TO WORK.
My recommendation is as a minimum to enable a MLUT for the viewfinder. If you wish to record S-Log3 to an external recorder then you should not add a MLUT to the SDI/HDMI output. But if you are using an external monitor purely for monitoring it may be desirable to enable an MLUT for the SDI/HDMI output.
The default MLUT is Sony’s s709 LUT. This is the same LUT as used by the Venice digital cinema camera. s709 is designed to be a starting point for a film style look. To achieve this film style look it uses brightness levels more commonly found in feature films rather than the levels normally used in the majority of regular TV shows.
LUT EXPOSURE LEVELS
There are some important things to understand about different MLUTs and Base Looks. Each MLUT/Look will have it’s own optimum brightness levels. They will not all be the same. Some will be brighter or darker than others when exposed correctly, so it’s vital that you understand what levels any MLUT that you chose to use needs to be exposed at.
Another MLUT that the FX6 includes is Sony’s 709(800) LUT. This MLUT is more closely aligned with the levels used in normal TV productions, so it looks quite different to s709 and has very different brightness levels when exposed correctly.
The chart below gives the “correct” exposure values for S-Log3 as well as some guide values based on my own measurements for the s709 and 709(800) MLUTs found in the FX6.
Average Skin Tones
90% Reflectivity white card (add 2-3% for white paper).
MEASURING THE EXPOSURE.
There are many ways to measure your exposure when shooting using S-Log3 and MLUT’s. You could choose to use a light meter, in which case the light meter would be set to match the EI (Exposure Index) value set in the camera.
You can just look at the image in the viewfinder and judge when it looks right. Most of the time this is going to be OK, but it isn’t particularly accurate and if shooting outside in bright sunshine it may be difficult to see an unshaded LCD screen correctly.
My preferred method is to use a white card or grey card and then use the cameras built in video signal monitor and the waveform display to actually measure the brightness of the grey card or white card.
Note: When referring to a “white” exposure this means the exposure level of a white card that reflects 90% of the light that falls on it. It is not how bright your highlights are, or how bright clouds are. It is the brightness of a diffuse white card. A piece of white paper or a white shirt can be used if you don’t have a proper white card, but be aware that white printer paper or white fabrics are treated with brightening agents to make them look “bright” so white paper and white fabrics will be a little brighter, perhaps 94% reflectivity compared to 90% of a proper white card and this should be allowed for.
The Waveform Display.
If you are not familiar with a waveform display it is actually really easy to understand. The bottom of the waveform is black and the very top is 109%, the brightest that the camera can ever record to.
The left hand side is the left of the video image and the right is the right side of the video image. The thin grey reference lines across the waveform display are at 0% (the darkest a video image should ever normally be), 25%, 50%, 75% and 100%.
In addition the FX6’s waveform display includes 2 yellow lines. The position of these yellow lines is determined by the levels that the cameras zebras are set to. By default the lower yellow line will be at 70% to match Zebra 1 and the upper line at 100% to match zebra 2.
WHAT ARE YOU MEASURING?
The waveform display measures the signal that is on the HDMI and the SDI output. So when you turn on the MLUT for the HDMI/SDI it is the levels of the MLUT that are being measured. If you don’t have an MLUT enabled for the SDI/HDMI then you will be measuring the recorded S-Log3 level. What the waveform is measuring is indicated just above the waveform display, in the example above we can see it is indicating LUT s709, so we are measuring the s709 LUT.
UNDERSTANDING HOW IT ALL WORKS.
To make it easier to understand how CineEI works I find it easier to start by turning OFF the LUT for the SDI and HDMI and measuring the exposure of the S-Log3. If you do this when the the Exposure Index (EI) is set so that it is equal to the Recording or Base ISO then you can use a white card or piece of white paper to establish the correct exposure for the S-Log3. Once you have done that you can then enable the MLUT and check the exposure of the LUT. So, lets see how we do that:
FIRST CHECK AND SET THE EXPOSURE INDEX LEVELS.
With the cameras base ISO set to low / 800 ISO I recommend that you set the EI levels in the main menu SHOOTING – ISO/Gain/EI as follows:
ISO/GAIN BUTTON and CHANGING THE EI:
When using the CineEI mode you can change the EI value several ways. The most commonly used ways will likely be via the L/M/H ISO/Gain switch or by pressing the ISO/Gain button and then using the multi-function dial (MFD) to change the EI. Do note that when you use the multi-function dial or Direct Menu to change the EI this new EI setting changes the preset value associated with the current position of the L/M/H switch.
Personally I do not usually set an Exposure Index value that is higher than the base recording ISO value. The reason for this is that as you will see later, if you record using a high EI value your images will be noisy and grainy and could be very difficult to grade. Because you don’t ever see your final results until you get into post production, if you accidentally record noisy log you won’t really know how bad the footage will be until it is perhaps too late to do anything about it. So I set the EI for the Low Base 800 ISO as H>800EI, M>400EI, L>200EI. The difference between each of these EI’s is one stop and sticking to exact 1 stop increments makes it easier when you are checking any exposure changes.
For the 12,800 High base ISO I set the EI to H>12800EI, M>6400EI, L>3200EI.
FOR THIS EXAMPLE START AT LOW BASE/800 ISO and 800 EI.
By using the same EI as the base recording ISO there will be no offset or difference between the aperture, ND or shutter speed settings used for the correct exposure of the LUT and the correct, or “base exposure” for the S-Log3. Expose the LUT correctly and the S-Log3 will be also be normally exposed. Expose the S-Log3 normally and the LUT will look correct.
FOR THIS EXAMPLE LET’S START WITH THE SDI/HDMI LUT OFF.
For this example I am going to start with the LUT OFF for the SDI and HDMI, this way the waveform display will be measuring the S-Log3. Just above the waveform it should say SG3C/Slog3, telling you the waveform is measuring the S-Log3.
Referring to the table of exposure levels earlier in this article we can see that the correct exposure for S-Log3 using a white card (90% reflectivity white) is 61% – if using a normal piece of printer paper I suggest using a value a little higher (around 63%) as white paper tends to be a little brighter than a proper white test card. So, when measuring the S-Log3 we want to expose a white card at 61%. We can use the cameras zebras to help us find 61%.
SETTING ZEBRA 1 TO 61%
To make finding where 61% is on the waveform I recommend setting Zebra 1 to 61% so that the lower of the two yellow zebra lines on the waveform display is at 61%.
So now when checking the exposure of a white card when the waveform is measuring the S-Log3, it is simply a case of adjusting the exposure until the white card is at the same level as the 61% line. Alternately you could use an 18% grey card, in which case you would set Zebra 1 to 41%, however there are often times when I forget my grey card but I almost always have a piece of paper somewhere.
So now we know that the S-Log3 is correctly exposed lets turn ON the LUT for the SDI and HDMI outputs and check the exposure level of the s709 LUT (or any other LUT that you wish to use – by setting the S-Log3 exposure first, you can then determine the correct exposure level of any LUT that you might wish to use).
NOW TURN ON THE SDI/HDMI LUT – DON’T CHANGE ANYTHING ELSE.
And if we refer to the exposure chart given towards the top of the page we will see that white for the s709 LUT is 77%. So now let’s set Zebra 2 to 77% to make 77% easier to find on the waveform. Do remember however that other LUTs may need different levels, 77% is just for s709, 709(800) would require Zebra 2 to be set to 89%.
SET ZEBRA 2 TO 77% FOR s709
Now with the LUT ON for the SDI/HDMI we should see the brightness of the white card line up with the upper yellow line that represents Zebra 2 and 77%.
As you can see from the above example when the Base ISO and Exposure Index are matched, in this case the base ISO is 800 and the EI is 800, when the LUT for the SDI/HDMI is OFF and the white card is at 61% on the waveform the S-Log3 is correctly exposed. Then when the s709 LUT is ON for the SDI/HDMI the white card will be at 77%. We are correctly exposed. By having Zebra 1 set at 61% (for S-Log3) and Zebra 2 set for the white level for for your chosen LUT we can check either simply by turning the HDMI/SDI LUT ON or OFF.
USING THE 709(800) LUT INSTEAD
If you want a more contrasty looking image in the viewfinder and similar brightness levels to other video cameras – for example skin tones around 70% you might prefer to use the 709(800) LUT. When using the 709(800) LUT to measure a white card you should set Zebra 2 to 89%. It’s also worth noting that with the 709(800) LUT, if you wish, you could just leave the zebras at their default settings with Zebra 1 at 70% where just like a conventional Rec-709 video camera they will appear over brighter skin tones when viewing via the LUT.
CHANGING THE EXPOSURE INDEX TO OFFSET THE LOG EXPOSURE.
Sometimes it can be desirable to expose the S-Log3 a little brighter. For example when shooting scenes with a low average brightness level or scenes with large areas of shadows. The FX6 has very low noise levels at 800 ISO base. So, for most scenes with high average brightness levels there is not normally any need to expose the log any brighter than the normal Sony recommended levels. There is however a bit more noise at 12,800 ISO base. As a result it can be beneficial to expose the S-Log3 a bit brighter than the base level when using 12,800 ISO base to help keep the noise in the final image low.
CineEI Allows Accurate Control Over Exposure.
The CineEI mode makes this very easy to do in a very controlled manner. Keeping the amount of over exposure constant helps speed up the grading process as all your material can be graded in exactly the same way.
Over exposing or underexposing Log does not change the captured dynamic range, it will always be the same. However exposing log brighter will reduce the highlight range while at the same time increasing the shadow range. A brighter exposure will result in less noise after grading.
Exposing log darker will increase the highlight range but decrease the shadow range. A darker exposure will result in more noise after grading. Because under exposed log can become very noisy, very quickly I do not recommend under exposing log, because of this I strongly advise against ever using an EI that is higher than the base ISO as this will result in under exposed log.
CHANGING THE EI ONLY CHANGES THE LUT.
When you change the Exposure Index the only thing that actually changes is the brightness of the LUT. So for EI to work you must be monitoring via a LUT.
Below is what happens to the image in the viewfinder when you have a LUT enabled (s709 in this case) and you lower the EI from 800 EI down to 200 EI in 1 stop steps and make no changes to the exposure.
Changing the EI does not change the exposure in any way, the only thing changing is the brightness of the LUT. The recording levels have not yet changed in any way.
BUT NOW WE CHANGE THE EXPOSURE
At a lower than than base EI the image in the viewfinder is dark and the white card no longer reaches the correct exposure for the LUT, because we see this dark image and the level of the white card too low we now adjust the exposure to compensate.
In this example I simply opened the aperture by 2 stops from f8 to f4 to match the 2 stop change in the LUT brightness. Now the image in the viewfinder looks correct again and the white card is meeting the upper yellow line again (77% as set by Zebra 2 level).
BECAUSE THE EXPOSURE IS BRIGHTER THE S-LOG3 IS NOW ALSO BRIGHTER.
Because I have opened the aperture by 2 stops to make the 200 EI LUT exposure look right the S-Log3 recordings will now be 2 stops brighter. If I turn off the LUT for the SDI/HDMI we can see that the S-Log3 that will be recorded is now 2 stops brighter, the S-log3 white card level becomes 79%, so it appears slightly above the 77% Zebra 1 line.
By making the LUT darker by 2 stops, then adjusting the exposure upwards 2 stops to return the LUT to the original brightness we have made our recordings 2 stops brighter. This is how you use CineEI to alter the brightness of your recordings. A lower EI leads to a darker LUT and because the LUT looks dark we increase the exposure making the recording brighter. A brighter recording will have less noise than a darker recording.
At Low base ISO (800 ISO) the FX6 is a low noise camera, so there is no need to routinely over expose the log as there is with more noisy cameras like the FS5 or FS7. So I normally shoot at 800 EI. When using the high base ISO or 12,800 ISO there is a bit more noise and when using high base I will typically set the EI to 6400 EI as the 1 stop brighter recordings that this will result in helps compensate for the increased recording noise.
DYNAMIC RANGE and HIGHLIGHT/SHADOW RANGE:
When you shoot with a low EI the LUT will be dark and as a result f the dark viewfinder image you will expose brighter putting more light onto the cameras sensor. This brighter exposure will decrease the amount of noise in the final image and give you a greater shadow range. But at the same time it will decrease the highlight range that can be captured.
If you use a high EI value then the opposite happens. The brighter viewfinder image and higher LUT levels will make you want to expose darker to compensate. The resulting darker S-Log3 recording will have an increased highlight range but it will be considerably more noisy than recordings done at the base EI and will have a reduced shadow range. Generally I try to avoid ever using an EI value higher than the base ISO value. In a low light situation using a high EI value will make the image in the viewfinder brighter but on a small screen you won’t see the noise. I do not recommend using high EI values.
IF YOU DON’T HAVE A WHITE CARD?
In the examples given here I have used a white card to measure and set the exposure. This is accurate and highly repeatable. But there will be times where you may not have a white card. At these times CineEI can still be used either by setting the Zebras to the appropriate skin tone levels for the chosen LUT (see the table towards the beginning) or by carefully “eyeballing” the brightness of the LUT image on the viewfinder screen or a monitor screen – if it looks right, it probably is right. If you are eyeballing it I highly recommend a deep sunshade or other device to exclude as much light as possible from the viewfinder. With a properly shaded viewfinder or monitor it is perfectly possible to shoot just by eyeballing the LUT’d image on the screen. As an exposure that is a little too dark is often going to cause more problems than an exposure that is a little too bright, if “eyeballing” the image I suggest using an EI that is 1 stop lower than the base EI. So in the case of the FX6 I would use 400 EI for low base ISO and 6400 EI for high base ISO.
CLIP PLAYBACK QUIRKS (YOU MUST ENSURE YOU HAVE UPDATED YOUR CAMERAS FIRMWARE as there was a bug in the initial release firmware that caused the playback EI to be applied back to front).
One great FX6 feature is that when you play back clips in the CineEI mode the camera can apply a LUT to the clip. Simply enable the LUT you want to use as you would when shooting. The FX6 applies then the EI offset that you have assigned to the L/M/H gain/ISO switch.
HOWEVER YOU DO THIS BE AWARE THAT THE L/M/H Gain switch alters the brightness of the clips when played back via a LUT. The only time there is no playback offset is when the switch is set to 800EI. So make sure you understand what EI it is you are looking at when playing back clips in CineEI as if you use the wrong EI your clips may appear over or under exposed.
I hope you found this guide useful. Good luck with your FX6, it is a very capable camera.
Changing the way the camera looks and using LUTs in Custom Mode:
You can also use any user LUTs that you have loaded into the camera to alter the base look when you are shooting in custom mode. For more information on that please watch the video below.
Here are the guide videos I produced for Sony about the FX9. These videos cover most of the key features of the camera whether that’s shooting using S-Cinetone or S-log3 and Cine EI, farme rates and scan modes. Each video includes instructions on how to use the different modes as well as some guidance on things to watch out for. Some of the videos were produced with version 1 firmware so there are now some changes to the base modes, previously you had Custom Mode and Cine EI, now you have SDR – HDR – CineEI where SDR mode is the same as what was previously called custom mode. Also don’t miss the two videos linked at the end which cover most of the new features added in the version 2 firmware.
Sony have released the PXW-FX9 user guide that I wrote for them. The guide is in the form of a searchable PDF designed for reading on a mobile device. The idea being that you can keep it on your phone in case you need to reference it on a shoot. It’s not meant to replace the manual but to compliment it and answer questions such as – what is S-Cinetone?
To download the guide go to the main Sony PXW-FX9 landing page and scroll down towards the bottom. There you should find a link that will take you to the guide download page as well as other resources for the FX9.
I was recently asked by Sony to write a user guide for the PXW-FS7 and FS7M2. Well it’s now complete and available for free download from Sony. The guide does not replace the manual but should act as a useful point of reference for those unfamiliar with the cameras. It should also help guide you through the use of the CineEI mode or change the various gammas settings in custom mode to suit different types of scene.
There are sections on exposure tools and controls, the variable ND filter, exposure tools and controls. Custom mode paint settings, Cine EI and LUT’s and additional information on the various shooting modes and functions.
There are two versions of the guide. One is an ePub book that can be displayed and read by may book reader programs such as iBooks and the other is an interactive PDF formatted for use on a mobile phone or tablet.
So with the FS7 now shipping and the first units landing in peoples hands I have put together a comprehensive guide to using S-Log3 and CineEI on the PXW-FS7. Please follow this link to read or download the guide to CineEI on the PXW-FS7.
It’s important to note that S-Log3 has a peak recording level of 92IRE so never goes above this. Don’t be surprised to find that your overall levels are going to be much lower than you would normally use for conventional 709 shooting. In addition I can’t stress enough how important it is to learn how to use LUT’s (look up tables) in camera and in post production with this camera. It will make your life so much simpler and easier. LUT’s may sound complicated and difficult, but they are not. If you want to create your own LUT’s take a look at this guide here.
The FS7 is an incredibly powerful camera. But if you really want to get the most from the Cine-EI mode and S-Log then you need to adjust the way you shoot. You can’t just apply normal Rec-709 exposure levels to S-Log3, it’s not designed to work that way. However by using the 709(800) LUT on the viewfinder output you can expose based on the viewfinder image as you would normally, while the S-Log3 recordings will be at the correct levels. So do learn how to implement LUT’s correctly, it will make your life so much easier. Take a look at this video for an idea of how it works. The video features an F5 but the FS7 is the same.
While you’re at it you might also want to take a look at this article on the S-log3 gamma curve. Many people will look at the S-log and think that it looks noisy and be worried by this. You shouldn’t be. The shape of the log curve means that before grading and application of a LUT it can emphasise noise. However once you use a LUT to convert from S-log3 to 709 you will find that most of the noise will go away. Again, please use a LUT as simply trying to grade S-log3 in to 709 space is often not as effective as adding the right LUT. If you really know what you are doing, by using S-Curves and log grading tools it is possible to grade the native S-log3 in a 709 environment, but LUT’s do make it simpler. Another useful way to get from S-log3 to 709 is to use the new color chart tool in Resolve which recognises and corrects either a Macbeth chart or DSC One Shot chart to the correct levels automatically. When you set up this process in Resolve you will select the source gamma as S-Log3 so the correction compensates for the gamma curve as well as adding color correction. I’lll write this up in more depth in the next couple of weeks.
So enjoy your FS7 if you have one. As soon as mine arrives I will write up the correct way (or at least the designed way) to use the Cine-EI mode, in the mean time the F5/F55 Cine-EI guide can be used, the process is exactly the same on the FS7.
Just a quick note to remind those eagerly waiting the arrival of their FS7 cameras that the CineEI mode of the FS7 is just about identical to the CineEI mode of the F5 and F55. SO if you want to know how it works then take a look at my guides to CineEI and LUT’s on the F5 and F55.
If you find this useful please consider buying me a coffee or a beer. I’m not paid to write these articles.
One of the really nice features of the Sony A7s and Sony’s other Alpha cameras, including the A6300, A6500 etc is the ability to use different gamma curves and in particular the Sony S-Log2 gamma curve.
What are gamma curves?
All conventional cameras use gamma curves. The gamma curve is there to make the images captured easier to manage by making the file size smaller than it would be without a gamma curve. When TV was first developed the gamma curve in the camera made the signal small enough to be broadcast by a transmitter and then the gamma curve in the TV set (which is the inverse of the one in the camera) expanded the signal back to a normal viewing range. The current standard for broadcast TV is called “Recommendation BT-709”, often shortened to Rec-709. This gamma curve is based on standards developed over 60 years ago and camera technology has advanced a lot since then! Even so, almost every TV and monitor made today is made to the Rec-709 standard or something very similar. Many modern cameras can capture a brightness range, also known as dynamic range, that far exceed the Rec-709 standard.
The limitations of standard gammas.
As gamma effects the dark to light range of the image, it also effects the contrast of the image. Normal television gamma has a limited dynamic range (about 6 to 7 stops) and as a result also has a limited contrast range.
Normally the gamma curve used in the camera is designed to match the gamma curve used by the TV or monitor. This way the contrast range of the camera and the contrast range of the display will be matched. So the contrast on the TV screen will match the contrast of the scene being filmed and the picture will look “normal”. However the limited dynamic range may mean that very bright or very dark objects cannot be accurately reproduced as these may exceed the gammas dynamic range.
The over exposure typical of a restricted range gamma such as Rec-709 is commonly seen as bright clouds in the sky becoming white over exposed blobs or bright areas on faces becoming areas of flat white. Objects in shade or shadow areas of the scene are simply too dark to be seen. But between the overexposed areas and any under exposure the contrast looks natural and true to life.
Log gamma, such as Sony’s S-Log2, allows the camera to capture a much greater brightness range or dynamic range than is possible when shooting with conventional television gamma. Dynamic range is the range from light to dark that the camera can capture or the range that the monitor or TV can display within one image. It is the range from the deepest blacks to the brightest whites that can be captured or shown at the same time.
There are some things that need to be considered before you get too excited about the possibility of capturing this much greater dynamic range. The primary one being that if the camera is set to S-log2 and the TV or monitor is a normal Rec-709 TV (as most are) then there is no way the TV can correctly display the image being captured, the TV just doesn’t have the range to show everything that the camera with it’s high range log gamma can capture accurately.
Fixed Recording Range For Both Standard and Log Gamma.
The signal range and signal levels used to record a video signal are normally described in percent. Where black is 0% and the brightest thing that can be recorded is normally recorded at 100% to 109%. Most modern video cameras actually record the brightest objects at 109%. The important thing to remember though is that the recording range is fixed. Even when you change gamma curve the camera is still constrained by the zero to 109% recording range. The recording range does not change whether you are recording Rec-709 or S-log2. So log gamma’s like S-Log2 must squeeze a much bigger signal range into the same recording range as used by conventional Rec-709 recordings.
In order to record using S-log2 with the A7s you need to use a picture profile. The picture profiles give you several recording gamma options. For S-log2 you should use Picture Profile 7 which is already set up for S-log2 and S-Gamut by default (for information on gamuts see this article). In addition you should ALWAYS use the cameras native ISO which is 3200 ISO and it is normally preferable to use a preset white balance. Using any other ISO with S-log2 will not allow you to get the full benefit of the full 14 stops of dynamic range that S-log2 can deliver. In most of the Alpha cameras you now also have the ability to use a different version of S-log, – S-Log3 and this is found in picture profiles 8 and 9. You can use S-Log3 if you wish, but S-Log2 was designed from the outset by Sony to work with digital camera sensors. S-Log3 is based on an older curve designed for film transfers to a 10 bit recording. As a result when using a camera that only has 8 bit recording with a limited number of code values, S-Log2 tends to be more efficient and yield a better end result. This is what it was designed for.
Grey Cards and White Cards.
Before I go further let me introduce you to grey and white cards in case you have not come across them before. Don’t panic you don’t have to own one, although I would recommend getting a grey card such as the Lastolite EzyBalance if you don’t have one. But it is useful to understand what they are.
The 90% White Card.
The 90% white card is a card or chart that reflects 90% of the light falling on it. This will be a card that looks very similar in brightness to a piece of ordinary white paper, it should be pure white, some printer papers are bleached or coloured very slightly blue to make them appear “brilliant white” (as you will see later in many cases it is possible to use an ordinary piece of white paper in place of a 90% white card for exposure).
The Grey Card.
The 18% grey card, also often called “middle grey” card, is a card that reflects 18% of the light falling on it. Obviously it will appear much darker than the white card. Visually to us humans an 18% grey card appears to be half way between white and black, hence it’s other name, “middle grey”.
Middle grey is important because the average brightness level of most typical scenes tends to be around the middle grey brightness value. Another key thing about middle grey is that because it falls in the middle of our exposure range it makes it a very handy reference level when measuring exposure as it is less likely to be effected by highlight compression than a 90% white card.
Exposing White and Middle Grey.
Coming back to Rec-709 and conventional TV’s and monitors. If we want a piece of white paper to look bright and white on a TV we would record it and then show it at somewhere around 85% to 95% of the screens full brightness range. This doesn’t leave much room for things brighter than a white piece of paper! Things like clouds in the sky, a shiny car, a bright window or a direct light source such as a lamp or other light. In order to make it possible for S-log2 to record a much greater dynamic range the recording level for white and mid tones is shifted down. Instead of recording white at 85%-95%, when using S-log2 or S-Log3 it is recommended by Sony that white is recorded at around 60%. For S-Log2 Middle grey moves down too, instead of being recorded at 42%-43% (the normal level for Rec-709) it’s recorded at just 32% with S-Log2 (S-log3 uses 41%).
By recording everything white (ie a white piece of paper) and darker in a lower range, we free up lot of extra space above the white recording level, within the full recording range, to record all those bright highlights in any scene that would be impossible to record with conventional gammas where there is only 10% to 20% from white at 90% to the peak of the recording range at 100 to 109%.
As S-Log2 and S-Log3 normally shift a lot of the recording levels downwards, if we show a scene shot with S-Log2 or S-log3 that has been exposed correctly on a conventional TV or monitor it will look dark due to the lower recording levels. In addition it will look flat with very low contrast as we are now squeezing a much bigger dynamic range into the limited conventional Rec-709 display range of a normal TV or computer monitor.
This on screen reduction in contrast and the darker levels are actually perfectly normal when shooting using log gamma, this is how it is supposed to look on a normal monitor or TV. So don’t be alarmed if when shooting using S-Log your images look a little darker and flatter than perhaps you are used to when shooting with a standard gamma. You will adjust the S-Log footage in post production to restore the brightness and contrast later.
The post production adjustment of S-Log2 and S-log3 is very important and one of the keys to getting the very best finished images. The S-Log recording acts as a digital negative and by “processing” this digital negative in post production (normally referred to as “grading”) we manipulate the large 14 stop dynamic range of the captured image to fit within the limited display range of a Rec-709 TV in a pleasing manner. This may mean pulling up the mid range a bit, pulling down the highlights and bit and generally shifting the brightness and colour levels of different parts of the image around (see PART 2 for more post production information).
SLog-2 and 10 bit or 8 bit data.
Originally Slog-2 was designed for use on high end digital cinema cameras such as Sony’s F65 camera. These cameras have the ability to record using 10 bit data. A 10 bit recording can have up to around 1000 shades of grey from black to white. The A7s however uses 8 bit recording which only has a maximum of 235 shades from black to white. Normally 8 bit recording is perfectly OK as most transmission and display standards are also 8 bit. Shoot with an 8 bit camera and then display that image directly via an 8 bit system and nothing is lost. However when you start to grade and manipulate the image the difference between 8 bit and 10 bit becomes more significant. If you start to shift levels around, perhaps stretching out some parts of the image then the increased tonal resolution of a 10 bit recording helps maintain the very highest image quality. Photographers that have shot using both jpeg and raw will know how much more flexibility the 12 bit (or more) raw files have compared to the 8 bit jpeg’s. However they will also know that 8 bit jpeg’s can be also adjusted, provided you don’t need to make very large adjustments.
Contrary to popular belief heavy grading of 8 bit footage does not necessarily lead to banding in footage across smooth surfaces except in extreme cases. Banding is more commonly a result of compression artefacts such as macro blocking. This is especially common with very highly compressed codecs such as AVCHD. The 50Mbps XAVC-S codec used in the Sony Alpha cameras is a very good codec, far superior to AVCHD and as a result compression artefacts are significantly reduced, so banding will be less of an issue than with other lower quality codecs. If you’re going to shoot using S-Log2, some grading will be necessary and as we only have 8 bit recordings we must take care to expose our material in such a way as to minimise how far we will need to push and pull the material.
Getting Your Exposure Right.
When S-Log2 was developed the engineers at Sony produced tables that specified the correct exposure levels for s-Log2 which are:
As you can see the nominal “correct” exposure for S-Log2 is a lot lower than the levels used for display on a typical Rec-709 TV or monitor. This is why correctly exposed s-log2 looks dark on a conventional TV. The implication of this is that when you grade your footage in post production you will have to shift the S-log2 levels up quite a long way. This may not be ideal with an 8 bit codec, so I decided to carefully test this to determine the optimum exposure level for the A7s.
The panel of images below is from the A7s recording S-log2 and exposed at the Sony recommended “correct” 32% middle grey level. The correct exposure was determined using a grey card and an external waveform monitor connected to the cameras HDMI output. Then the S-log2 was corrected in post production to normal Rec-709 levels using a Look Up Table (LUT – more on LUT’s in part 2). You can also see the viewfinder display from the camera. If you click on the image below you can expand it to full size. Sorry about the shadow from the laundry line, I didn’t see this when I was shooting the test shots!
From this you can see just how dark and low contrast looking the original correctly exposed S-log2 is and how much more vibrant the corrected Rec-709 image is. I have also indicated where on the cameras histogram middle grey and white are. Note how much space there is to the right of white on the histogram. This is where the extra highlight or over exposure range of S-log2 can be recorded. When correctly exposed S-log2 has an exposure range of 6 stops above middle grey and 8 stops under.
Over Exposing or “Pushing” S-log2.
If we deliberately raise the exposure level above the Sony recommended levels (known as pushing the exposure), assuming you grade the image to the same final levels some interesting things happen.
For each stop we raise the exposure level you will have 1 stop (which is the same as 6db) less noise. So the final images will have half as much noise for each stop up you go. This is a result of exposing the image brighter and as a result not needing to raise the levels in post as far as you would if exposed at the normal level.
You will loose one stop of over exposure headroom, but gain one stop of under exposure headroom.
Bright highlights will be moved upwards into the most compressed part of the log gamma curve. This can result in a loss of texture in highlights.
Skin tones and mid tones move closer to normal Rec-709 levels, so less manipulation is need for this part of the image in post production.
This last point is important for the A7s with it’s 8 bit codec, so this is the area I looked at most closely. What happens to skin tones and textures when we raise the exposure?
Exposing at +1, +2 and +3 Stops.
Below are another 3 panels from the A7s, shot at +1 stop, +2 stops and +3 stops. Again you can click on the images if you wish to view them full size.
Looking at these results closely you can see that when you increase the exposure by 1 stop over the Sony specified correct level for S-log2 there is a very useful reduction in noise, not that the A7s is particularly noisy to start with, but you do get a noticeably cleaner image.
Below are 4 crops from the same images, after grading. I really recommend you view these images full size on a good quality monitor. Click on the image to view larger or full size.
The noise reduction at higher exposures compared to the base exposure is very clear to see if you look at the black edge of the colour checker chart (the coloured squares), although the difference between +2 and +3 stops is very small. You can also see further into the shadows in the +3 stop image compared to the base exposure. A more subtle but important effect is that as the exposure goes up the visible texture of the wooden clothes peg decreases. The grain can be clearly seen at the base level but by +3 stops it has vanished. This is caused by the highlights creeping into the more compressed part of the log gamma curve. The same thing is happening to the skin tones in the +3 stop image, there is some reduction of the most subtle textures.
From this we can see that for mid tones and skin tones you can afford to expose between 1 and 2 stops above the Sony recommended base level. More than 2 stops over and brighter skin tones and any other brighter textures start to be lost. The noise reduction gain by shooting between one and 2 stops over is certainly beneficial. The down side to this though is that we are reducing the over amount of exposure headroom.
Given everything I have seen with this 8 bit and almost every other 8 bit camera my recommendation is to shoot between the Sony recommended base S-log2 level and up to two stops over this level. I would try to avoid shooting more than 2 stops over as this is where you will start to see some loss of texture in brighter skin tones and brighter textures. Exactly where you set your exposure will depend on the highlights in the scene. If you are shooting a very bright scene you will possibly need to shoot at the Sony recommended level to get the very best over exposure headroom. If you are able to expose higher without significantly compromising any highlights then you should aim to be up to 2 stops over base. But whatever you do never expose darker than the Sony base level, this will normally look really nasty.
Determining The Correct Exposure.
The challenge of course is determining where your exposure actually is. Fortunately as we have seen, provided you in the right ball park, S-log2 is quite forgiving, so if you are a little bit over exposed it’s probably not going to hurt your images much. If you have a waveform monitor then you can use that to set your exposure according to the table below. If you don’t have proper white or grey cards you can use a piece of normal white paper. Although slightly less accurate this will get you very close to where you want to be. Do note that white paper tends to be a little brighter than a dedicated 90% reflectivity white card. If you don’t have any white paper then you can use skin tones, again a bit less accurate but you should end up in the right zone.
If you don’t have an external waveform monitor then you do still have some good options. Sadly although the camera does have zebras, these are not terribly useful for S-log2 as the lowest the zebras can go is 70%.
Light Meter: You could use a conventional photography light meter. If you do choose to use a light meter I would recommend checking the calibration of the light meter against the camera first.
Mark 1 Eyeball: You could simply eyeball the exposure looking at the viewfinder or rear screen but this is tricky when the image is very flat.
In Camera Metering: The cameras built in metering system, like the majority of DSLR’s is calibrated for middle grey. By default the camera uses multi-point metering to measure the average brightness of several points across the scene to determine the scenes average brightness and from there set the correct base S-log2 exposure.
When you are using S-Log2, auto exposure in most cases will be very close to the correct base exposure if you use the default Multi-Zone exposure metering. The camera will take an average exposure reading for the scene and automatically adjust the exposure to the Sony recommended 32% middle grey exposure level based on this average. In the P, A and S modes you can then use the exposure compensation dial to offset the exposure should you wish. My recommendation would be to add +1 or +2 stops via the dial. Then observe the histogram to ensure that you don’t have any significant over exposure. If you do then reduce the exposure compensation. Lots of peaks to the far right of the histogram is an indication of over exposure.
Manual Exposure And Internal Metering.
If you are exposing manually you will see a small M.M. indication at the bottom of the LCD display with a +/- number. In the eyepiece viewfinder this appears as a scale that runs from -5 to +5, in S-log2 only the -2 to +2 part of the scale is used. In both cases this is how far the camera thinks you are away from the optimum exposure. + meaning the camera is over exposed, – meaning under.
In the image above we can see the M.M. indication is +0.3, in the eyepiece you would see a small arrow one bar to the right of “0” , indicating the cameras multi zone metering thinks the shot is just a little over exposed, even though the shot has been carefully exposed using a grey card and external waveform monitor. This error is probably due to the large amount of white in the shot, white shirt, white card, test charts with a lot of brighter than grey shades. In practice an error of 0.3 of a stop is not going to cause any real issues, so even if this was exposed by setting the exposure so that you have “M.M. 0.0” the exposure would be accurate enough. But it shows that multi point exposure averaging is easily confused.
The scene above is a fairly normal scene, not excessively bright, not particularly dark. If shooting a snow scene for example the cameras multi point averaging would almost certainly result in an under exposed shot as the camera attempts to bring the bright snow in the scene down to the average middle grey level. If shooting a well lit face against a very dark background then the averaging might try to bring the background up and the shot may end up overexposed.
If you want really accurate exposure then you should put the cameras metering system into the spot metering mode where instead of taking an average of various points across the scene the camera will just measure the exposure at the very center of the image.
You can then use a grey card to very accurately set the exposure. Simply place the circular shaped symbol at the center of the viewfinder display over a grey card and set the exposure so that M.M is 0.0 for the correct S-Log2 base exposure. To expose 1 stop over with a grey card, set M.M. +1.0 and two stops over M.M. +2.0 (not flashing, flashing indicates more than +2 stops).
One small issue with this is that the camera will only display a M.M. range of -2.0 to +2.0 stops. Provided you don’t want to go more than 2 stops over base then you will be fine with a grey card.
Using White Instead of Grey:
If you don’t have a grey card then you can use a 90% reflectivity white target. As white is 2 stops brighter than middle grey when S-Log2 is correctly exposed the 90% white should indicate M.M +2.0.
Once you have established the correct exposure you can then open the iris by 1 or two stops to increase the exposure. Or halve the shutter speed to gain a one stop brighter exposure. Each time you halve the shutter speed your exposure becomes one stop brighter, so divide the shutter speed by 4 to gain a 2 stop increase in exposure. As always you should observe the histogram to check for any over exposure. White peaks at the far right of the histogram or disappearing completely off the right of the histogram is an indication of over-exposure. In this case reduce your exposure back down towards the base exposure level (M.M 0.0 with a a grey card).
I recommend using an exposure between the “correct” base S-Log2 exposure level of middle grey at 32% and two stops over this. I would not recommend going more than 2 stops over over base.
In the P, A and S auto exposure modes, when using the default multi-zone metering the camera will set the base S-log2 exposure based on the average scene brightness. For most typical scenes this average should be very close to middle grey. This exposure can then be increased (brightened) by up to 2 stops using the exposure compensation dial.
In manual exposure the “M.M.” number displayed at the bottom of the viewfinder display is how far you are from the correct base S-log2 exposure. M.M. +2.0 indicates +2 stops over base. If using multi zone metering (the cameras default) this exposure will be based on the scenes average brightness.
If you set the metering to “Spot” you can use a grey card centred in the image to determine the correct base exposure and up to 2 stops of over exposure via the M.M. indication when shooting manually.
In Part 2:
In part two I will take a look at grading the S-log2 from the A7s and how to get the very best from the S-log2 images by using Look Up Tables (LUT’s).
Don’t forget I run storm chasing and Northern Lights expeditions every year. These are amazing expeditions by snowmobile up on to the Finnmarksvidda. We go ice fishing, dog sledding, exploring, cook a meal in a tent and enjoy traditional Norwegian saunas.
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