Tag Archives: colorspace

Workflow

More on Adobe’s new color managed workflow.

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I’ve written about this before, but the way Adobe have changed the way they manage colourspaces has changed, it hasn’t been well documented, and it’s causing a lot of confusion.

When importing Log footage into the latest versions of Adobe Premiere instead of the log footage looking flat and washed out as it used to, now it looks contrasty and well saturated. If it has been exposed correctly (according to the manufacturers specifications) then it will look like normal Rec-709 footage rather than the flat look that most people associate with log. This is confusing people, many assume Adbe is now adding a LUT to the footage by default, it isn’t. What is happening isd a fundamental change to the way Premiere handles different colorspaces.

NOT ADDING A LUT.

Premiere is NOT adding a LUT. It is transforming between the captured colorspace and the display colorspace so that the footage looks correct with the right contrast, colour and brightness on your display. Your footage remains in its native colorspace at all times (unless you force it into an alternate and possibly wrong colorspace by using the interpret footage function).

Your display could be 709, HDR10, HLG, SGamut3/S-log3 and in each case the footage would, within the limitations of the displays format have the same basic contrast and colour etc, the footage would look the same whether viewing in SDR, HDR or Log because Premiere maps it to the correct levels for the output colorspace you are using to view your content.

OLD BROKEN WORKFLOWS.

The issue is that previously we have been using very broken workflows  that are normally incapable of showing capture colorspaces other than Rec-709 correctly. This has made people believe that log formats are supposed to look flat – They are not! When viewed correctly they should  have the same contrast as 709 etc. Log is not flat, but we have been viewing it incorrectly because most workflows have been incapable of mapping different source colorspaces to our chosen working/viewing colorspace.

LUTs ARE A QUICK FIX – WITH LIMITATIONS.

Up to now to fix these broken workflows we have added LUT’s to convert our beautiful, high dynamic range, vast colorspace source formats into restricted, reduced dynamic range display formats. Once you add that 709 LUT to you S-Log3 footage it is no longer SGamut3/Slog3 it is now Rec-709 with all the restrictions that 709 has such as limited dynamic range, limited colorspace etc and that may limit what you can do with it in the grade. Plus it limits you to only ever outputting in SDR 709.

But what we have now in a colour managed workflow is our big range log being displayed correctly on a 709 display or any other type of display, including HDR or DCI-P3 etc. Because the footage is still in its native colorspace you will have much greater grading latitude, there’s no knee added to the highlights, no shadow roll off, no artificial restriction to the source colorspace. So you can more easily push and pull the material far further during adjustment and grading (raw workflows have always been color managed out of necessity as the raw footage can’t be viewed correctly without first being converted into a viewable colorspace).

HERE’s THE RUB!

But the rub is – you are not now adding someone else’s carefully crafted LUT, which is a combination of creative and artistic corrections that give a pleasing look combined with the Log to Rec 709 conversion.

So – you’re going to have to learn how to grade for yourself – but you will have a much bigger colour and contrast range to work with as your footage will remain in it’s full native capture range.

And – if you need to deliver in multiple formats, which you will need to start doing very soon if you are not already, it is all so much easier as in a colour managed workflow all you do is switch the output format to change from 709 to HDR10 or HLG or DCI-P3 to get whatever format you want without having to re-grade everything or use different LUT’s for each format.

HOW LONG CAN YOU STAY JUST IN REC-709?

And when you consider that almost all new TV’s, the majority of new Phones and Tablets all have HDR screens and this is all now supported on YouTube and Vimeo etc how much longer do you think you will be able to cling on to only delivering in SDR Rec-709 using off-the-shelf SDR LUTs? If you ever want to do stuff for Netflix, Amazon etc you will need to figure out how to work in both SDR and HDR.

IT’S HERE TO STAY

Adobe have done a shockingly bad job of documenting and explaining this new workflow, but it is the future and once you learn how to use it properly it should improve the quality of what you deliver and at the same time expand the range of what you can deliver.

I have to deliver both SDR and HDR for most of my clients and I’ve been using colour managed workflows for around 6 years now (mostly ACES in Resolve). I could not go back to the restrictions of a workflow that doesn’t allow you to output in multiple colorspaces or requires you to perform completely separate grades for SDR and HDR. The great thing about ACES is that it is a standardised and well documented workflow so you can use ACES LUT’s designed for the ACES workflow if you wish. But until Adobe better document their own colour managed workflow it is difficult to design LUT’s for use in the Adobe workflow. Plus LUT’s that work with the Adobe workflow, probably won’t work elsewhere. So – it’s never been a better time to learn how to grade properly or think about what workflow you will use to do your grading.

The bottom line is the days of using LUT’s that add both an artistic look and convert your footage from its source colorspace to a single delivery colorspace are numbered.  Color managed offer far greater flexibility for multi format delivery. Plus they retain the full range and quality of your source material, no matter what colorspace you shot it in or work in.

cameras, cinematography, Technology, Workflow

Will a bigger recording Gamut give me more picture information?

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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.

Gamuts-only Will a bigger recording Gamut give me more picture information?

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”.

S-log-levels Will a bigger recording Gamut give me more picture information?
Chart showing S-Log2 and S-Log3 plotted against f-stops and code values. Note how little data there is for each of the darker stops, the best data is above middle grey. Note that current sensors only go to +6 stops over middle grey so S-Log2 and S-Log3 record to different peak levels.

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.