ACES Color Space

[Jadefox]

Hi all

Can I kindly ask what the fuss is about ACES ?
I understand that its a standardized color space and of such importance that its set to default.
For me however the render becomes way too dark and overly contrasted. which makes me think I have setup light and textures very wrong for the last few years.
Do any of you actually make use of it or immediately untick and proceed with older color space ?

Looking forward to some responses.

[piotrus3333]

are you talking about ACES OT layer in tonemapping layer stack?

[maru]

Hi all

Can I kindly ask what the fuss is about ACES ?
I understand that its a standardized color space and of such importance that its set to default.
For me however the render becomes way too dark and overly contrasted. which makes me think I have setup light and textures very wrong for the last few years.
Do any of you actually make use of it or immediately untick and proceed with older color space ?

Looking forward to some responses.

Please note that the "ACES OT" operator in the tone mapping stack is NOT a color space. It is an "output transformation" which is basically an advanced version of a LUT. It only changes the appearance of your image to make it look photographic, and nothing else. If you don't like it, you can simply disable it, just like LUT, or any other tone mapping / post-processing effect.

There were no changes to the internal color space Corona is using for a very long time. There are no new color space defaults in Corona 8 or 9.

[Jadefox]

yeah apologies , I meant in the stack.
Ok I just wanted to double check if everybody makes use of it and if so how do you guys make use of it.

[TomG]

Switch it on if you like the look, off if you don't :) It doesn't change color space at all.

[romullus]

At first i didn't liked Aces OT that much, i felt that my old tone mapping settings doing better job, but gradually new tone mapping grew on me, especially since i changed my monitor to a better one and now i use default Corona tone mapping settings almost all the time. I feel that Corona is finally at the stage where it is good enough without any post processing, or other magic in 99% cases. But that's just me, there's nothing wrong in turning off Aces OT if you don't like it.

[piotrus3333]

yeah apologies , I meant in the stack.
Ok I just wanted to double check if everybody makes use of it and if so how do you guys make use of it.

It's just a very popular tone mapping operator. Mimics linear srgb to display srgb transform from aces system. One thing to remember is to add 1 stop of exposure before ACES OT to match exposure of older scenes using some other tone mapping approach. If the image does not look at least ok with +1 exp and ACES OT then something is most likely not right with shaders/lighting.

more about this 1 stop difference here:
https://forum.corona-renderer.com/index.php?topic=35847.msg199786#msg199786

[maru]

At first i didn't liked Aces OT that much, i felt that my old tone mapping settings doing better job, but gradually new tone mapping grew on me, especially since i changed my monitor to a better one and now i use default Corona tone mapping settings almost all the time. I feel that Corona is finally at the stage where it is good enough without any post processing, or other magic in 99% cases. But that's just me, there's nothing wrong in turning off Aces OT if you don't like it.

Fun fact: with older versions of Corona, I used a maxstart scene with custom tone mapping to make my sample images look "nice" out of the box (some filmic mapping, contrast, and saturation changed). Later it turned out that my custom defaults were giving reeeeeally similar results to just having a single ACES OT operator enabled.

[Juraj]

At first i didn't liked Aces OT that much, i felt that my old tone mapping settings doing better job, but gradually new tone mapping grew on me, especially since i changed my monitor to a better one and now i use default Corona tone mapping settings almost all the time. I feel that Corona is finally at the stage where it is good enough without any post processing, or other magic in 99% cases. But that's just me, there's nothing wrong in turning off Aces OT if you don't like it.

Fun fact: with older versions of Corona, I used a maxstart scene with custom tone mapping to make my sample images look "nice" out of the box (some filmic mapping, contrast, and saturation changed). Later it turned out that my custom defaults were giving reeeeeally similar results to just having a single ACES OT operator enabled.

Same :- ). It lacked wow factor for me since I already had nice curve and desaturating LUT in my stack. But now it slowly grows on me.

[busseynova]

I noticed the ACES OT option kills dynamic range in a 16bit file. Does anyone have it as a LUT so it can be placed at the top of a stack in photoshop instead?

[alexyork]

I noticed the ACES OT option kills dynamic range in a 16bit file. Does anyone have it as a LUT so it can be placed at the top of a stack in photoshop instead?

This is an ongoing struggle for us too. ACES really is a great look and saves time, but at a pretty hefty expense of losing any ability to re-expose the EXR/CXR afterwards (plus the annoyance of ACES double-tonemapping when you open a render in CIE). I have a love/hate relationship with it, basically.

[piotrus3333]

I noticed the ACES OT option kills dynamic range in a 16bit file. Does anyone have it as a LUT so it can be placed at the top of a stack in photoshop instead?

that is not true.
please see attached. original acesot from CIE (png16) and said original (as jpg) that went through transform back to linsrgb (exr16f with dwaa lossy compression for good measure) and again "acesot" to display:

[image used: https://acescentral.com/knowledge-base-2/using-aces-reference-images/]

[alexyork]

Not sure what your example is showing but I don't think it's what busseynova or I are referring to. If you use ACES (at 1.0, say, since that's the default), and render an EXR, load that into Photoshop and try underexposing it - you can't - whites go grey. Now if you do the same without using ACES (or any other kind of highlight compression) you can successfully underexpose the render in Photoshop and loads of data is retained. I understand (from chats with Tom/Corona guys) why this is happening, and it's not a bug, but it's still a workflow issue/hindrance. The "gold standard" would be to have ACES (or ACES-like) tone mapping but still retain the same (or similar) level of dynamic range in the rendered result.

The best example to test this on is a simple scene using corona sun and sky, with the sky slightly overexposed in the base render by say 1 stop. If your EXR has proper dynamic range then you can very easily recover that in post and expose down to reveal the sun showing clearly and the sky becomes blue etc. as you would expect from for example a CR2/DNG RAW photo. When using ACES this ability is removed, as you'll just darken the base render without revealing any more data, and that's the issue.

[pokoy]

But the same would've happened with Filmic/Reinhard prior to ACES in Corona.

There was another thread where the request was to apply tone mapping as a display transform only so the saved data would still have the full dynamic range.
Obviously, this means that the image you save has no tone mapping applied, essentially disabling the entire tone mapping post section... you can't have both at the same time.

[piotrus3333]

Not sure what your example is showing but I don't think it's what busseynova or I are referring to. If you use ACES (at 1.0, say, since that's the default), and render an EXR, load that into Photoshop and try underexposing it - you can't - whites go grey.

my example is showing that you do not lose much dynamic range saving with acesot.
edit: acesot preserves the range up to 16 (and a bit) float

you are trying to underexpose the exr with baked acesot (32bit mode, multiplication operation in photoshop) by one stop. so multiply by 0.5 - if your brightest highlight is 1 (acesot) than 1/0.5 = grey.
reverse the transform: srgb display to linsrgb, expose with multiplying linear data, go back to acesot (aces' srgb display odt). fnord had ocio plugin for ps. or make some luts for -1EV, +0.5EV etc. or maybe even curves presets.