Author Topic: OFFICIAL Q/A: sRGB, gamma, color pickers, linear workflow, ...  (Read 49405 times)

2016-11-16, 18:29:49
Reply #15

astudio

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Hi Dubcat.

Nice if you get displacement map from scaner. But it's not usual case in real work.
For example palm bark from evermotion looks completely flat comparing to real palms in our area. The question is what to do if I'd like to edit displacement map?

I made it in 8 bit before (attached), but after your threads about megascans and substance I think that 32 Bit will give me better result. So what to do?

2016-11-16, 19:29:34
Reply #16

dubcat

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Project the 8bit map in a sculpting program (eyeball intensity, since all the real data is gone).
Do the changes + 8bit clean up.
Export as 32bit.

But you know, in reality we can't do this to every single shitty displacement map out there, and intensity is all we have.
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2016-11-16, 20:21:07
Reply #17

astudio

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Here is a point. As was noted by Romullus in my tests (attached before) photoshop gives wrong RGB values when you export to 32 Bit and it leads to wrong displacement values.  It's clearly visible in render. What program can I use for correct export to 32 Bit?

2016-11-16, 21:03:37
Reply #18

romullus

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If you only want to convert your 8bit or 16bit displacement textures to 32bit and you think that doing that will somehow increase their quality, then don't bother, it won't. You can't add more information to map just by increasing its bit depth. You could do like dubcat suggested, displace geometry by low bith depth texture, tweak/fix/resculpt mesh and then properly bake displacement map from that geometry to 32bit texture, but the amount of work required for such operation, means that it's feasible only for single cases, unless you could find a way how to automate this process.
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2016-11-17, 00:12:18
Reply #19

astudio

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Not, of course. I'd like to manage 32 bit images, not just convert. This way I may to get incredible things from one plane only. Just need to learn to draw in 32 bit, for getting in 10 minutes exactly what you expect. ;) 
But there is for another thread. Thank you.
« Last Edit: 2016-11-17, 00:39:55 by astudio »

2017-07-07, 12:42:40
Reply #20

maru

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Link to a helpdesk article created based on this forum thread: https://coronarenderer.freshdesk.com/support/solutions/articles/12000020988
(it's basically the same thing, just re-organized a bit, and with image examples)
Marcin Miodek | chaos-corona.com
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2019-04-04, 11:39:43
Reply #21

Hilmar

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Hi
I have one question to all this different gamma loading thing.... I used to load the Maps as following: diffuse-leave it at 2.2, and gloss/ref/bump/normal/displacement with "overide 1.0" assuming they are all saved as JPGs. But, if I use a taken photo of a Surface and mix this in photoshop/quixel or substance to a bump or normal map and save that one as JPG …. do I have to use Gamma 1 as well, because it was degamma.ed when loading in PS?

Thanks in advance



2019-06-13, 09:33:51
Reply #22

siavash82ir

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hi friends
Here is a point. As was noted by Romullus in my tests (attached before) photoshop gives wrong RGB values when you export to 32 Bit and it leads to wrong displacement values.
 It's clearly visible in render. What program can I use for correct export to 32 Bit?

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« Last Edit: 2019-11-04, 17:54:59 by siavash82ir »

2020-07-19, 11:55:40
Reply #23

monitorhero

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Sorry for replying to such an old thread but strange things are happening on my end and I can't really wrap my head around it.
So in Photoshop I create a pure red color field in sRGB Profile (which is standard setting in PS). I put R 255 G 0 B 0. Save it as a file. (attached it here)
If I open this bitmap in 3dsmax and open image in Max I get a value of R 253 G 0 B 0.
Not it gets worse. If I use a Vray color map and pick the color with Corona Color Picker from the bitmap field in the Material Editor I get a value of R 254 G 0 B 0.
Wait. It gets better. Now if I pick the color directly from Photoshop I get a color that has R 220 G 14 B 7.

However if I set my Photoshop Color Management to Monitor RGB now I can pick the correct color. But as a saved bitmap it still has a value of R 253 G 0 B 0.

Please help! :D

2022-11-26, 19:37:48
Reply #24

VIZSET

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Hello! I'm trying to export exr image into DavinciResolve and get incorrect color input.
In Corona output ACES is on, in Davinci project color management settings I choose ACES too. EXR settings in MAX by default. Where am i doing wrong?
« Last Edit: 2022-11-26, 19:44:34 by VIZSET »
More works: behance.net/vizset

2022-11-28, 14:23:28
Reply #25

TomG

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Remember that the ACES OT checkbox does NOT make the image into ACES colorspace - it only applies the ACES "sweetener curve" to the image. The output EXR is not then in ACES colorspace.
Tom Grimes | chaos-corona.com
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2022-11-28, 14:50:06
Reply #26

maru

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@VIZSET as Tom explained, the ACEST OT operator in the Corona tone mapping stack is something like an advanced version of a LUT, which just makes your image look nice.

Could you please explain what exactly is your problem? You are saving an image from the Corona VFB, loading it into Davinci Resolve, and you are getting different colors?
Marcin Miodek | chaos-corona.com
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2022-11-29, 09:36:43
Reply #27

VIZSET

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@VIZSET as Tom explained, the ACEST OT operator in the Corona tone mapping stack is something like an advanced version of a LUT, which just makes your image look nice.

Could you please explain what exactly is your problem? You are saving an image from the Corona VFB, loading it into Davinci Resolve, and you are getting different colors?

Hello!
Yes, problem with different colors when I save an exr from VFB and import it to DaVinci (when ACES OT on or off - it's doesn't matter). Importing the same exr to photoshop goes correctly.
More works: behance.net/vizset

2022-12-09, 17:18:44
Reply #28

maru

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@VIZSET as Tom explained, the ACEST OT operator in the Corona tone mapping stack is something like an advanced version of a LUT, which just makes your image look nice.

Could you please explain what exactly is your problem? You are saving an image from the Corona VFB, loading it into Davinci Resolve, and you are getting different colors?

Hello!
Yes, problem with different colors when I save an exr from VFB and import it to DaVinci (when ACES OT on or off - it's doesn't matter). Importing the same exr to photoshop goes correctly.

I did some quick checks:

Rendered a colorful scene similar to yours (strongly colored lights, objects, enviro).
Also added an invisible box casting shadow to see a dark gradient (this is great for testing sRGB vs 2.2 gamma - you can see the difference in shadows).

Opened the VFB as a reference.
Saved as 32-bit EXR.
Opened in Chaos Player with "color space" set to "default" - the shadows are visibly darker.
Opened in Photoshop - the shadows are visibly darker.
Opened in DaVinci Resolve 18.1.1 (the Fusion tab) - by default the image is clearly displayed in linear color space and gamma 1.0. Hence the huge change in the overall brightness and color appearance. I tried "fixing it" to look the same as in Chaos Player and PS so I clicked LUT at the top of the viewport and selected VFX IO > Linear to sRGB. I did not measure this, but in my opinion it looks exactly like the result from Chaos Player and PS.


What happens (I am not an expert so I could make some mistake here, but it should be correct):

Corona VFB:
3ds Max is not color managed.
Corona uses Adobe Wide RGB color space internally (you can change it in devel/experimental stuff rollout - https://support.chaos.com/hc/en-us/articles/4528523195537).
Then the image is displayed in the VFB with gamma 2.2 (this is specified in 3ds Max settings).

Chaos Player and PS:
The EXR is opened and displayed with sRGB gamma which is slightly different than gamma 2.2 - this is why there are small differences mostly between the darkest areas.

I also tried to get exactly the same result in DaVinci as in the Corona VFB, but I don't know DaVinci well enough. I *think* the way to do it would be:
- load the EXR
- set input color space to Adobe RGB (I am not sure if this is correct, I could not find this option)
- then set output gamma to 2.2 (not sRGB)

I hope this helps.



Marcin Miodek | chaos-corona.com
3D Support Team Lead - Corona | contact us

2022-12-10, 18:39:45
Reply #29

piotrus3333

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@VIZSET
just tell DaVinci that exr from Corona is lin sRGB.

@ Corona Team
how about calling a spade a spade? ACES OT is Corona's version of lin srgb to display srgb transform from ACES OCIO config. you slapped "aces" name on it after all. this would simply help to avoid confusion.
Marcin Piotrowski
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