V-Ray 5 | SelfIllum in LgtMtl and VRayMtl different for 32Bit TextureMaps

[JonasNöll]

Hi, I'm having an issue where the same map in the LgtMtl and VRayMtl looks different with LgtMtl being incorrect and VRayMtl is correct.
Problem ONLY occurs with 32bit channel images such as this EXR, if I convert it to JPG it looks the same for both.
If I use a VRayBitmap instead of Bitmap same issue, also when cycling through the different color transfer modes, the both look different,
VRayMtl has a 0% diffuse and only Self-Illumination applied with Multi of 1. VRayLgtMaterial also has Multi of 1. Both don't compensate for cam exposure.

Is this a bug or for some reason intentional?

[hermit.crab]

I tried reproducing the issue with a 32-bit baked checker map to no avail. Could you attach the scene here so we can take a look? Share your V-Ray and host platform versions as well.

[JonasNöll]

Hi, I think I found the issue. Both started to look correct when I switched the alpha source within the VRayBitmap to "none". Then I checked the image file and found that somehow the alpha channel had intensity values higher than 1, such as 1,97.
In this case then the VRayLightMtl is mixing the texture with the inverse of the color value. Once I clamped the values in the alpha to a value of 1 everything worked fine, no matter if chosing an alpha source or not.
No idea though how those values in the alpha could become higher than one though, as the exr I was using was just saved out of the V-Ray framebuffer earlier witout any modifications...