What does Spectral Conversion Color Space actually do?

mark212160

What does Spectral Conversion Color Space actually do?

According to Omniverse Materials and Rendering documentation, Spectral Conversion Color Space has the effect as follows - 

For the conversion of color data to spectra, the rendering core needs to know the

color space the data is defined in. Supported color spaces are:

CIE XYZ (xyz)

Rec.709/linear sRGB (rec709)

Rec.2020 (rec2020)

ACES2065-1 (aces)

ACEScg (acescg)

Note: This option also comes into play when spectral data is used without spectral rendering enabled.

In these cases, it defines the conversion of spectra to colors to be used for rendering.

Does this mean that if I set Spectral Conversion Color Space to ACEScg, Iray will automatically convert sRGB input textures to ACEScg color space and output 32-bit linear ACEScg EXR files if I also have Canvases enabled?
So far, I already know how to batch convert textures to ACEScg, but how do I specify Iray to output renders in ACEScg color space since the default is always linear sRGB?

I appreciate any replies, but please make sure you 100% know what you are talking about, as topics regarding digital colors are already quite confusing to me.

Unseen

You can find more information  on the spectral conversion color space in this blog post:

https://www.daz3d.com/blog/best-iray-settings-for-daz-studio?srsltid=AfmBOoov_hXr6Oi4TOH0y6XNfhNncodr93uKLvxLLSjAuLZ766K7gMTz

Scroll down to Spectral Rendering.

mark212160

Unseen said:

You can find more information  on the spectral conversion color space in this blog post

I have already read that blog post before, and the information they provided is no different than the one from Omniverse Materials and Rendering documentation.
I am more concerned about the output color space.
You can specify Iray to interpret textures in the ACEScg color space (assuming you convert the textures to ACEScg beforehand), but how do you make it output the renders in the same color space?
Additionally, is there any view transform function that I can utilize to properly examine the ACEScg textures inside the Iray viewport through my sRGB monitor?

prixat

I think DAZ or Iray or both went for the simplest method and have automatic transforms into and out of the render space. You won't see anything other than sRGB in the viewport.

Try taking the canvasses into something like Affinity:

https://www.daz3d.com/forums/discussion/440567/help-ocio-open-color-io-for-post-processing?srsltid=AfmBOopeZBSaz08EdwjZ4CEjn-o8XEtoFAn1Bg7BeDQ4YMVIVBcmZEbF

mark212160

prixat said:

I think DAZ or Iray or both went for the simplest method and have automatic transforms into and out of the render space. You won't see anything other than sRGB in the viewport.

I have done my own test.

If I set Spectral Conversion Color Space to ACEScg and render the output as an EXR with sRGB textures. The render will look wrongly oversaturated in Photoshop after setting the working color space to ACEScg.

If I set Spectral Conversion Color Space to ACEScg, plug in the converted textures, which I have confirmed to be in ACEScg color space in Photoshop, and render the output as an EXR. The render will still look wrong in Photoshop after setting the working color space to ACEScg.

This test shows that Iray does not automatically match the input color space. Instead, it reverses its ACEScg calculation back to its default linear sRGB when outputting renders, even if they are in EXR format.

The solution provided from your link is not what I want. I want Iray to be able to preserve as much color information as possible when outputting renders. That is why I chose ACEScg and why I specified wanting Iray to output renders in that specific color space, instead of the default linear sRGB.