Linear-sRGB not behaving as expected

Well said Thomas. Amen.

Is that something that can be done with OCIO? My understanding was that since the RRT and ODT have been combined into a single LUT that it was not possible to remove the RRT.

Here’s a thought: Based on what you say above “the RRT should present images with less contrast and should be more “averagely average”, to be frank, I actually prefer ARRI’s K1S1 which is less aggressive”

and this here which echos what I was noticing with the green Emily above in my OP"

“The ACES Reference Rendering Transform has a distinct look that I think isn’t very natural. The RRT has an extreme shoulder that extends down towards the midtones, reducing saturation and shifting skin tones towards green.”

and this here

“Ideally, the RRT should not exist, or should at least be neutral, imparting no predetermined ‘Look’ onto the image…Ideally, the ODT should take images directly from ACES space, with no RRT involvement.”

What if the RRT was removed and instead there was an LMT where one could put the RRT filmic tone curve or if desired one could put something less aggressive like you mentioned. That way one would still be able to have an s-shaped curve (which I think we both agree is very important for rendering), but would not have a particular “look” imposed on the filmmaker (which is just as important for artists to have tools that allow artists to achieve their vision rather than imposing one on them).

The thing to understand is that as soon as you do something on the image, you are imposing a Look on it. Not doing anything is also akin to pick a Look, i.e. a Non-Look Look. Basically, there is no such thing as No Look.

It is easier to find negative commentary online about something rather than positive. People tend to grab the pen more often in case of problems rather than when everything is awesome.

I think that the ACES RRT is rather appreciated, if not, ACEScentral would have attracted negative comments about it via all the Unreal Engine developers, which are millions, yes, many millions :slight_smile: Brian Karis, who implemented ACES support in UE4 really likes it. I will not quote him but he was super positive. Now, importantly, he introduced a tiny technical transformation: he over-exposed everything with a gain of 1.45, i.e. a gain LMT, that was all that was required to satisfy the artists at Epic Games. This implementation is being used successfully by most of the UE4 developers since a few years now. My gut feeling is that this was needed because most artists are working under viewing conditions that are simply too bright and are used to the sRGB No Look.

When I say that I’m “in the camp of people thinking that the RRT should present images with less contrast and should be more “averagely average””, I’m saying it while assessing ACES imagery on a multiple thousands dollars display, calibrated with a colorimeter costing even more and under relatively well-controlled Viewing Conditions that are metered and tuned accordingly. When I’m confident that my entire viewing environment is appropriate to review imagery, only then I allow myself to express subjective creative comments.

With that in mind, it is effectively critical that your viewing environment is appropriate, thus a few questions:

  • What is your display?
  • How is it calibrated?
  • What are your viewing conditions? Can you give me illumination information at your desk?

Another critical point if you are using sRGB, is that most consumer displays adopt a naive and simple 2.2 Gamma EOTF approximation instead of the piece-wise function defined in the IEC 61966-2-1:1999 Standard. It will result in the decoding of ACES imagery for sRGB which effectively crushes blacks:

If you remember, I actually commented that the OP Emily right image was looking fine to me, I was reviewing it in my calibrated environment but are you? One recommendation I could do is to try to look at ACES imagery under Theatrical Exhibition Viewing Conditions to appreciate the original Look intent.

All that to say, that I think you should try to use the system as it is intended first and under a proper viewing environment. See where it falls short in your context, and then proceed with incremental and small changes as required. However, I would never ever go as far as changing the whole RRT. It was designed under perfect viewing conditions and if you don’t have access to a Theatre or DI suite, you will probably do worse than better.

@jim_houston was involved significantly in the RRT design and might have extra recommendations to offer.

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Let me clarify that I am not advocating for removing the RRT, nor am I advocating for changing it (well maybe I am a little bit there). But mostly I am advocating making it more modifiable by decoupling it from the ODT so one would have the option of leaving it as is or possibly tweaking it, if one wanted for example something less aggressive. In other words, I’m advocating for choice.

Ha! :slight_smile: Hard to think this is not the case when reading What if the RRT was removed and instead there was an LMT where one could put the RRT filmic tone curve or if desired one could put something less aggressive like you mentioned.

The RRT is already decoupled from the ODT by design, this is exactly how the system works and in that design, an LMT prior to the RRT is the prescribed way to modify the Look. Note that the new SSTS will effectively couple them but this is another discussion.

If you need something less aggressive, that is where you put a contrast reduction or a gain, like Epic did.

I notice that you haven’t answered my questions about your viewing environment, those are the most important things to address before doing anything else.

Yes that’s a fair point.

Okay, I’ll certainly look into that with the tone curve, but are you also suggesting that this would be a way to undo the color shifts of the sweeteners? I thought you had said earlier (post 7) that that wasn’t really possible.

As far as answering your questions:

  • What is your display? sRGB
  • How is it calibrated? sRGB
  • What are your viewing conditions? random/varied

So you might say I’m the consumer-grade scenario, while you have optimized ideal viewing conditions. But the stated goal of ACES is to have an image look good in ideal and also in non-ideal conditions, for it to look good in the theater, but also for it to look good on Netflix on a laptop, right? :slight_smile:

Gamma 2.2 or sRGB? :wink:

The mission is to deliver images that look great under the supported viewing environments, i.e. the ones covered by the ODTs, the assumption though is that the viewers adhere to them, if not, well, one cannot expect the system to deliver good results.

Thanks for all your input Thomas, it gives me a lot of food for thought. Hope you have a great weekend