The short answer is it all depends on the camera you are using. With the F55 or F65 then S-Log2/S-Gamut and S-Log3/S-Gamut3 will give you a larger range of colours in your final image than S-Log3/S-Gamut3.cine. But if you have a PMW-F5, PXW-FS7 or PXW-FS5 this is not going to be the case.
What is Gamut?
The word Gamut means the complete range or scale of something. So when we talk about Gamut in a video camera we are talking about dynamic range and color range (colorspace) taken together. Then within the Gamut we can break that down into the dynamic range or brightness range which is determined by the gamma curve and the color range which is determined by the colorspace.
Looking at the current Sony digital cinema cameras you have a choice of 3 different gamuts when the camera is in log mode plus a number of conventional gamuts you get when shooting rec-709, rec-2020 or any other combination of rec-709 color with cinegammas or hypergammas.
Log gamma and gamuts.
But it’s in the log mode where there is much confusion. When shooting with log with the current cameras you have 3 recommended combinations.
S-Gamut (S-Gamut colorspace + S-log2 gamma).
S-Gamut3 (S-Gamut3 colorspace + S-Log3 gamma).
S-Gamut3.cine (S-Gamut3.cine colorpace + S-Log3 gamma).
The S-log2 and S-log3 gamma curves both capture the same dynamic range – 14 stops, there is no difference in the dynamic range captured.
In terms of the range of colors that can be recorded S-Gamut and S-Gamut3 are the same size and the largest recording colorspaces the cameras have. S-Gamut3.cine is a smaller colourspace but still larger than P3 (digital cinema projection) or rec-709.
But those were all designed for the F55 and F65 cameras that have extremely high quality (expensive) colour filters on their sensors. The reality is that the F5/FS7/FS5 sensor cannot see the full range of any of the S-Gamut colorspaces so in reality you gain very little by using the larger versions. Don’t expect to see a noticeably greater range of colours than any of the other colour modes if you have the F5/FS7/FS5. But all the LUT’s designed for these cameras are based on the S-Gamuts and if you want to mix an FS5 with an F55 in one production it helps to use the same settings so that grading will be easier. It is worth noting at this point that most natural colors do fall within Rec-709, so while it is always nicer to have a bigger color range it isn’t the end of the world for most of what we shoot.
S-Log3 is a great example of what it means to have a bigger recording range than the camera can “see”. S-log3 is based on the Cineon film transfer log gamma curve developed back in the late 1980’s. Cineon was carefully tailored to match film response and designed around 10 bit data (as that was state of the art back then). It allows for around 16 stops of dynamic range. Much later, Arri and many others then adapted Cineon for use in video cameras – The “C” in Arri’s LogC stands for Cineon.
When Sony started doing wide dynamic range cameras they developed their own log gammas starting with S-Log, then S-Log2. These curves are matched very precisely to the way a video sensor captures a scene rather than film. In addition they are matched to the sensors actual capture range, S-Log can record 13 stops as that’s what the sensors in the cameras with S-Log can see. Then S-Log2 is 14 stops as the second generation cameras can all see 14 stops. As a result of being purpose designed for a video sensor, when using S-Log2 you maximise the entire recording range because the sensor is matched to the log which is matched to the record range.
But, these curves drew much criticism from early adopters and colorists because they were very different from the Cineon curve and all the other log curves based on this old school film curve. Colorists didn’t like it because none of their old Cineon LUT’s would work as expected and it was “different”.
In response to this Sony then developed S-Log3 and surprise, surprise – S-log3 is based on Cineon. So S-log3 is based on a 16 stop film transfer curve, but the current cameras can only see 14 stops. What this means is that the top 14% of the gamma curve is never used (that’s where stops 15 and 16 would reside) and as a result s-Log3 tops out at 92% and never gets to the 107% that S-Log2 can reach. If Sony were to release a 16 stop camera then S-Log3 could still be used and then it would reach 107%.
Coming back to colorspace. If you understand that the sensor in the F5/FS7/FS5 cannot see the full colour range that S-Gamut or S-Gamut3 are capable of recording then you will appreciate that like S-log3 (that is larger than the camera can see and therefore part empty) many of the possible code values available in S-Gamut are left empty. This is a waste of data. So from a colourspace point of view the best match when shooting log for these cameras is the slightly smaller colorspace S-Gamut3.cine. But S-Gamut3.cine is meant to be matched with S-Log3 which as we have seen wastes data anyway. If the camera is shooting using a 10 bit codec such as XAVC-I or XAVC-L in HD there are plenty of code values to play with, so a small loss of data has little impact on the final image. But if you are recording with only 8 bit data, for example XAVC-L in UHD then this does become much more of a problem and this is when you will find that S-Gamut with S-Log2 is going to give a better result as S-Log2 was designed for use with a video sensor from day 1 and it maximises the use of what little data you have.
This keeps cropping up time and time again.
Unfortunately every now and again a new term or buzzword comes along that gets taken as a holy grail term. Two that come to mind right now are log and raw. Neither log, nor raw, are magic bullet solutions that guarantee the best performance. Used incorrectly or inappropriately both can result in inferior results. In addition there are many flavours of log and raw each with very different performance ranges.
A particular point in case is the 12 bit raw available from several of Sony’s mid range large sensor cameras, the FS700, FS7 and FS5.
Raw can be either log or linear. This particular flavour of raw is encoded using linear data. If it is linear then each successively brighter stop of exposure should be recorded with twice as many code values or shades as the previous stop. This accurately replicates the change in the light in the scene you are shooting. If you make the scene twice as bright, you need to record it with twice as much data. Every time you go up a stop in exposure you are doubling the light in the scene. 12 bit linear raw is actually very rare, especially from a camera with a high dynamic range. To my knowledge, Sony are the only company that offer 14 stops of dynamic range using 12 bit linear data.
There’s actually a very good reason for this: Strictly speaking, it’s impossible! Here’s why: For each stop we go up in exposure we need twice as many code values. With 12 bit data there are a maximum of 4096 code values, this is not enough to record 14 stops.
If stop 1 uses 1 code value, stop 2 will use 2, stop 3 will use 4, stop 4 will use 8 and so on.
STOP: CODE VALUES: TOTAL CODE VALUES REQUIRED.
+1 1 1
+2 2 3
+3 4 8
+4 8 16
+5 16 32
+6 32 64
+7 64 128
+8 128 256 Middle Grey
+9 256 512
+10 512 1,024
+11 1,024 2,048
+12 2,048 4,096
+13 4,096 8,192
+14 8,192 16,384
As you can see from the above if we only have 12 bit data and as a result 4096 code values to play with, we can only record an absolute maximum of 12 stops of dynamic range using linear data. To get even 12 stops we must record the first couple of stops with an extremely small amount of tonal information. This is why most 14 stop raw cameras use 16 bit data for linear or use log encoded raw data for 12 bit, where each stop above middle grey (around stop +8) is recorded with the same amount of data.
So how are Sony doing it on the FS5, FS7 etc? I suspect (I’m pretty damn certain in fact) that Sony use something called floating point math. In essence what they do is take the linear data coming off the sensor and round the values recorded to the nearest 4 or 8. So, stop +14 is now only recorded with 2,048 values, stop +13 with 512 values etc. This is fine for the brighter stops where there are hundreds or even thousands of values, it has no significant impact on the brighter parts of the final image. But in the darker parts of the image it does have an impact as for example stop +5 which starts off with 16 values ends up only being recorded with 4 values and each stop below this only has 1 or two discreet levels. This results in blocky and often noisy looking shadow areas – a common complaint with 12 bit linear raw. I don’t know for a fact that this is what they are doing. But if you look at what they need to do, the options available and you look at the end results for 12 bit raw, this certainly appears to be the case.
Meanwhile a camera like the FS7 which can record 10 bit log will retain the full data range in the shadows because if you use log encoding, the brighter stops are each recorded with the same amount of data. With S-Log2 and 10 bit XAVC-I the FS7 uses approx 650 code values to record the 6 brightest stops in it’s capture range reserving approx 250 code values for the 8 darkest stops. Compare this to the linear example above and in fact what you will see is that 10 bit S-Log2 has as much data as you would expect to find in a straight 16 bit linear recording below middle grey (S-Log 3 actually reserves slightly more data for the shadows). BUT that’s for 16 bit. Sony’s 12 bit raw is squeezing 14 stops into what should be an impossibly small number of code values, so in practice what I have found is that 10 bit S-log has noticeably more data in the shadows than 12 bit raw.
In the highlights 12 bit linear raw will have more data than 10 bit S-log2 and S-Log3 and this is borne out in practice where a brightly exposed raw image will give amazing results with beautiful highlights and mid range. But if your 12 bit raw is dark or underexposed it is not going to perform as well as you might expect. For dark and low key scenes 10 bit S-Log is most likely going to give a noticeably better image. (Note: 8 bit S-log2/3 as you would have from an FS5 in UHD only has a quarter of the data that 10 bit has. The FS5 records the first 8 stops in 8 bit S-log 2 with approx 64 code values, S-Log3 is only marginally better at approx 80 code values. 12 bit linear outperforms 8 bit log across the entire range).
Sony’s F5 and F55 cameras record to the R5 and R7 recorders using 16 bit linear data. 16 bit data is enough for 14 stops. But I believe that Sony still use floating point math for 16 bit recording. This time instead of using the floating point math to make room for an otherwise impossible dynamic range they use it to take a little bit of data from the brightest stop to give extra code values in the shadows. When you have 16,384 code values to play with you can afford to do that. This then adds a lot of extra tonal values and shades to the shadows compared to 10 bit log and as a result 16 bit linear raw will outperform 10 bit log across the entire exposure range by a fairly large margin.
So there you have it. I know it’s hugely confusing sometimes. Not all types of raw are created equal. It’s really important to understand this stuff if you’re buying a camera. Just because it has raw it doesn’t necessarily mean an automatic improvement in image quality in every shooting situation. Log can be just as good or possibly even better in some situations, raw better in others. There are reasons why cameras like the F5/R5 cost more than a FS5/Shogun/Odyssey.
I’ve written about this many times before, but still it comes up again and again. Which is better? Which should I use? I hear all kinds of crazy comments and a lot of incorrect information, so first of all lets dispel a few myths:
S-Log2 captures more dynamic range than S-Log3, it goes to a higher level on the waveform.
S-Log2 and S-Log3 both currently record exactly the same dynamic range as this is limited by the sensors that Sony are using. The S-log3 curve could be used in a future camera to capture up to 16 stops, but that camera does not exist at the time of writing. As the S-Log3 curve is designed to go beyond 14 stops, stop No. 14 is recorded at a lower level to allow space for up to 2 more stops. S-Log2 is a 14 stop maximum curve, so the peak level is much higher. In Sonys current camera range the limit is 14 stops whether it’s S-Log2 or S-Log3. The chart that Sony provide showing both S-Log2 and S-Log3 is a little confusing as it shows the entire gamma curve rather than what the camera can actually “see”. In their current implementations both curves stop at +6 stops over middle grey, both capture the same dynamic range, there is no difference.
S-Log2 is brighter than S-Log3 so it must be capturing highlights better.
No, not really, see above. Playback and on screen brightness comes from the levels chosen to record something at and is dependant on the shape and range of the gamma curve. But the actual captured range is dependant on what the sensor can cope with. As we are not changing the sensor, the captured dynamic range, brightness range and shadow range does not change between S-Log2 and S-log3, both of which take the entire sensor range (they just store that same range using slightly different levels). After applying a LUT or other conversion to your normal viewing gamma both S-Log2 and S-log3 will have the same brightness, same highlight and same shadow range.
S-Log3 has noisy shadows.
No, not really. Shadows appear noisy with S-Log3 as the shadow part of the curve is stored using higher code values compared to S-Log2. So when you view S-Log3 uncorrected the shadows are raised and stretched on your conventional monitor and this gives the impression of a noisy picture. In reality once you restore the levels to normal there is no additional noise. See this article for a full explanation.
S-Log3 is newer than S-Log2 so it must be better.
Newer, perhaps not. Better, no not really. S-Log3 is based on the industry standard Cineon log gamma curve. This curve was developed in the late 1980’s to allow the digitising of film using 10 bit data. So S-Log3 matches a curve designed to work with negative film and is capable of storing more than the 14 stops that the current cameras sensors can see. In effect it is an old log gamma curve. As it is a curve designed for more than 14 stops, when used in a 14 stop camera some of the available recording data is empty and wasted.
S-Log2 was specifically designed by Sony to work with an electronic sensor with 14 stops of dynamic range and is optimised to match the performance characteristics of video sensors. By using a 14 stop curve with a 14 stop camera almost every bit of available data is utilised, there is no wastage.
BUT THERE ARE SOME OTHER FACTORS WE NEED TO CONSIDER.
S-Log2 and S-Gamut:
As well as the gamma curve we also have different Gamuts or color ranges. S-Log2 was originally designed for the F65 camera. The F65 sensor can capture a huge color range beyond the range that most conventional video sensors can see. So as well as S-Log2 Sony introduced S-Gamut which was matched to the very wide color range of the F65 sensor. S-Log2 is designed to be used with S-Gamut. But many of the cameras we use, like the FS7, F5, FS5 cannot see this color range (Sony’s F55 can). In addition this very large color range can be a little tricky to deal with in post production. Add to this the fact that S-Log2 is quite different to the quite common Cineon gamma curve and as a result behaves differently in post. The end result was that there were a number of complaints and comments that Sony’s S-log2 material was difficult to grade.
S-Log3 and S-Gamut3.
Because some people were struggling a bit with S-Gamut and S-Log2 in post production (Resolve and many of the other tools we have today were not as well developed 4 years ago), Sony introduced S-Gamut3 and S-log3 as well as a further Gamut called S–Gamut3.cine. S-Log3 was based on Cineon as that’s what people were familiar with. Arri’s Log-C is also based on Cineon as are many other log curves. This makes it a more “familiar” grading experience for many colorists. In addition Sony created a modified version of the super large S-Gamut to make it easier to grade. S-Gamut3 is just as big as S-Gamut but some tweaks inside make it easier to grade (fewer color shifts). At the same time Sony realised that most users were producing content for TV, the web or digital cinema that had little use for the huge color range of S-Gamut/S-Gamut3. So S-Gamut3.cine was developed as a smaller, more manageable version of S-Gamut3 and it incorporated a few tweaks to the color science to provide colors closer to those used by other manufacturers. S-Gamut3.cine is also a better match for cameras with sensors that cannot see the full S-Gamut range (like the FS5, FS7, F5, A7).
The end result is that in general most people prefer or find it easier to grade S-Log3/S-Gamut3.cine material than S-Log2/S-Gamut. Plus you can often use LUT’s designed for Log-C or Cineon with S-log3 material (this isn’t optimum, but it can work).
Getting the data from camera to post.
In terms of getting the data from your cameras sensor in to post production S-Log2 is the better choice. It is optimised for the way an electronic sensor works. S-log3 is essentially a curve designed for negative film applications, not video and no matter how you look at it, these are electronic video cameras. However if you are recording 10 bit or greater you have a lot of data whichever curve you use, so in practice it will be rare to see any difference in the final result.
So use the curve you find easiest to work with. It is true that S-Log 3 allocates a little more data to the shadows and less to the highlights than S-Log2, but don’t confuse data and code values with more range. S-Log3 has a few extra code values in it’s darkest stops, S-log2 has a few extra in the bright stops, but the dynamic range, highlight and shadow handling is governed by the sensor not the gamma curve. Overall S-Log3 has fewer code values than S-Log2, S-Log2 makes better use of the data available, but with 10 bit this really isn’t going to make a huge difference.
8 Bit Recording.
But if you are only recording with an 8 bit codec you are already at a disadvantage. When recording 8 bit you really need to maximise the way what little data you have is used. For that reason I will always recommend that S-Log2 is used when recording 8 bit on a camera like the FS5 in UHD or A7s or similar (FS5 is 10 bit in HD). By using S-Log2 you are using as many of the limited code values available as you can. This doesn’t mean you can’t use S-log3, it just wouldn’t be my choice.
The end result should be the same.
At the end of the day, if you were to use matching LUTs, S-log2 and S-log3 material should look more or less exactly the same after grading or application of the LUT, no matter what the scene you are shooting. If they do look significantly different then you are doing something wrong. So your choice of curve, other than for 8 bit recordings will most likely come down to ease of use rather than anything else.
If your camera doesn’t have LUT’s then S-Log2 can be easier to work with as it is more contrasty. This makes it a bit easier to focus and also makes it easier to gauge exposure. If your camera has LUT’s and you use them, then you may decide to use S-Log3 simply because you should find it a little easier to work with in post. Either way both curves capture the same range of picture information and both should give more or less the same end result.
There may be some very, very subtle differences due to the small differences in data distribution, but often these will be hard to really see in the final image.
UPDATE: It appears that Adobe may have now addressed this. Luma and YC scopes now show the same levels, not different ones and the scaling of S-Log XAVC. signals now appears to be correct.
This came up as the result of a discussion on the FS5 shooters group on Facebook. An FS5 user shooting S-log2 was very confused by what he was seeing on the scopes in Adobe Premiere. Having looked into this further myself, I’m not surprised he was confused because it’s also confused me as there is some very strange behaviour with S-Log2 XAVC material.
First: BE WARNED THE “LUMA” SCOPE APPEARS TO BE A RELATIVE LUMINANCE SCOPE AND NOT A “LUMA” SCOPE.
THIS IS THE “LUMA” Scope, I suggest you don’t use it! Look at the scale on the left side of the scope, it appears to be a % scale, not unlike the % scale we are all used to working with in the video world. In the video world 100% would be the maximum limit for broadcast TV, 90% would be white and the absoulte maximum recording level would be 109%. These % (IRE) levels have very specific data or code values. For luma, 100IRE has a code value of 940 in 10 bit or 235 in 8 bit. Then look at the scale on the right side of the luma scope. This appears to be an 8 bit code value scale, after all it has those key values of 128, 255 etc.
Now look again at the above screen grab of the lumetri luma scope in Premiere 2017 – V11. On the left is what appears to be that familiar % scale. But go to 100% and follow the line across to where the code values are. It appears that on these scopes 100% means code value 255, this is not what anyone working in broadcast or TV would expect because normally code value 255 means 109.5%.
I suggest you use the YC waveform display instead.
The YC waveform shown on the above screen capture is of an S-Log2 frame. If you go by the % scale it suggests that this recording has a peak level of only 98% when in fact the recording actually goes to 107%.
But here’s where it gets even stranger. Look at the below screen capture of another waveform display.
So what is going on here? The above is a screen grab of Cinegamma 1 recorded in UHD using 8 bit XAVC-L. It goes all the way up to 109% which is the correct peak level for Cinegamma 1. So why does the S-Log2 recording only reach 98% but the Cinegamma recording, recorded moments later using the same codec reach 109%. This is a value 10% higher than S-Log2 and I know that the Cinegammas cannot record at a level 10% greater than S-Log2 (the true difference is only about 2%).
Lets now compare the difference between how Premiere and Resolve handle these clips. The screen grab below shows the S-Log2 and Cinegamma 1 recordings side by side as handled in Adobe Premiere. On the left is the S-Log2, right Cinegamma1. Look at the very large difference in the peak recording levels. I do not expect to see this, there should only be a very small difference.
Now lets look at exactly the same clips in DaVinci Resolve. Note how much smaller the difference in the peak levels is. This is what I would expect to see as S-Log2 gets to around 107% and Cinegamma 1 reaches 109%, only a very small difference. Resolve is handling the files correctly, Premiere is not. For reference to convert 8 bit code values to 10 bit just multiply the 8 bit value by 4. So 100IRE which is CV235 in 8 bit is CV940 in 10 bit.
So, until I get to the bottom of this all I can say is be very, very careful and don’t use the “Luma” scope, use the YC scope if you want to know your code values. It also appears that Premiere scales the code values of S-Log recordings differently to normal gammas.
Additionally: Record exactly the same S-Log2 or S-Log3 image using XAVC internally in the camera and at the same time record a ProRes version on an external recorder. Bring both of these clips, which are actually recorded using exactly the same levels into Premiere and Premiere handles them differently. The XAVC squashed into a reduced range while the ProRes fills the larger range.
This has huge implications if you use LUT’s!!!!
The same LUT will result in a very different looking image from the XAVC and PRoRes material. There should not be a difference, but there is and it’s big. So this isn’t just a scopes issue, it’s an internal signal handling issue.
I’ve always preferred doing my color grading in a dedicated grading package with external scopes. It’s stuff like this that reminds me of why I prefer to work that way. I always end up with a better end result when I grade in Resolve compared to Premiere/Lumetri.
As I learn more about this I will post a new article. Use the subscribe button on the left to subscribe to the blog to be notified of new posts.
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 new Sony A6300 is making quite a stir. This compact interchangeable lens camera has an amazing feature set that is very similar to the features found on it’s bigger brothers the A7sII and A7RII.
As a video camera it’s also capable recording using the XAVC-S codec in both HD and UHD(4K). It can even shoot at 120fps in HD. It also has picture profiles so you can tailor the look of the pictures or to suit different shooting conditions. The Cinegammas are very useful for challenging lighting conditions as they offer an improved highlight roll-off. As well as the Cinegammas the camera also has the S-Log2 and S-Log3 log gamma curves as well as S-Gamut, S-Gamut3 and S-Gamut3.cine.
Log gamma curves are very different to conventional gamma curves. Conventional gamma curves (like rec-709 or Cinegamma) are designed to produce a pleasing on screen image without any post production work (although the cinegammas do typically benefit with some tweaking in post). To do this conventional gammas keep the mid-range contrast compatible with conventional TV’s and monitors, so the picture has natural contrast when viewed on a TV. Then to help deal with bright highlights conventional gammas use some kind of highlight roll off or knee to increase the brightness range the camera can capture without effecting the mid range. Unfortunately this means that the highlights are somewhat compromised, looking very flat, lacking contrast and this is often what gives video the “video look”. In addition it also means that if you are over exposed when you shoot, the picture will look bad and no amount of post production correction will ever make it look good. Most TV camera operators will be very familiar with the phrase “protect your highlights”, meaning don’t over expose, if anything under expose a tiny bit to keep the highlights looking good.
Log gamma curves such as S-Log2 and S-Log3 are very different. They extended the dynamic range that the camera can capture. To do this they no longer try to be directly compatible with conventional TV’s and monitors and just focus on capturing the biggest possible range. The pictures will be made compatible with the TV or monitor via adjustments made during editing or in post production. So working with S-log2 and S-Log3 is a two step process – shooting and grading (grading is the term used for adjusting the look of an image in post production).
Because log gamma no longer needs to have a contrast range that matches the display range, more dynamic range can be squeezed into a conventional recording codec. It also means that there is no longer a need to use any highlight roll off or knee, so there is a lot more picture information in the highlights and brighter parts of the image. As a result exposing log gamma extra brightly is not normally a problem and in many cases brings lot of advantages. Log gamma curves do have a shadow roll off that mimics the real world shadow roll off. As a result log gammas really don’t like being under exposed, instead they prefer to be over exposed. So unlike conventional gamma where we “protect the highlights” with log gamma you need to “protect the shadows”. Under exposed log looks bad. It will lack color and it will be noisy and grainy.
For most camera operators it’s quite disconcerting to start shooting very slightly over exposed as it goes against everything you’ve learnt about shooting with a conventional video camera. But trust me, shooting 1 to 2 stops brighter than the recommended levels given by Sony on the A6300 (and any other Sony Log camera) will normally bring the best results.
I wrote a guide on how to do this with the Sony A7s here: http://www.xdcam-user.com/2014/08/exposing-and-using-slog2-on-the-sony-a7s-part-one-gamma-and-exposure/
The very same techniques can be used with the A6300, A7SII and A7RII. The A6300 etc also have S-Log3, but as these are 8 bit cameras (even when using an external recorder) I would still recommend that you use S-Log2. Besides, viewing and monitoring S-Log3 is tough as the pictures look even flatter than S-Log3.
If you follow the link below you will find a set of LUT’s (Look Up Tables) that can be applied to A6300 footage in post production to give different looks. There are some film-look LUT’s and 709 (normal TV look) LUT’s and in each case there are LUT’s for normal exposure as well as footage exposed 1 stop and 2 stops brighter. If a LUT name includes “1OVER” this means that the LUT is designed to work with footage that has been exposed 1 stop brighter than the levels given by Sony. My recommendation is to shoot at between 1 and 2 stops bright. For both S-Log2 and S-Log3 this would mean setting zebras to 70% and exposing a piece of white paper so that zebras are just starting to appear on the white paper.
If you find these LUT’s useful please consider buying me a coffee or a beer. I’m not paid to write these articles. For the LUT set I would appreciate a Cocktail, but am happy with whatever you feel is appropriate or affordable.
Damn, I just purchased a Sony A6000 to take to Norway next week and this pops up. It’s the latest camera in the compact camera range from Sony that started with the NEX-5 and NEX-3, great little cameras that take great photos and have been timelapse work-horses for me.
The A6300 specs are beyond impressive. It has a new 25MP sensor with an improved type of construction that improves sensitivity. It’s only APS-C so I’m not expecting A7 MK2 performance, but it should do very well when the light levels are low.
One of the headline features for me though is it’s ability to shoot 4K XAVC-S that is originated from a 6K image coming off the sensor. On top of that this truly pocket sized camera has what appear to be the full compliment of cinegammas as well as S-log2 and S-log3. Now before everyone gets too excited, do remember that XAVC-S is 8 bit whether in HD or SD, but even so this is an amazing feature set for this kind of camera.
If that isn’t enough it can even shoot in HD at upto 120fps!
The price? Well the body only is $999 USD. It’s E-Mount so as usual you can put all kinds of lenses on it from Sony power zooms to PL mount primes and everything in between. For more information on what on paper at least appears to be a remarkable little camera click here.
Ultimate Guide to CineEI on the PXW-FS7 (Updated May 2016).
This guide to Cine-EI is based on my own experience with the Sony PXW-FS7. There are other methods of using LUT’s and CineEI. The method I describe below, to the best of my knowledge, follows standard industry practice for working with a camera that uses EI gain and LUT’s.
If you find the guide useful, please consider buying me a beer or a coffee. It took quite a while to prepare this guide and writing can be thirsty work.
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.