Color rings in 1.5RC3?

[edgemedia]

Hello all, I've been following the threads for splotches (ErikCamper, et al) and tried all the settings (HSp 200, Lele's Irr -7/0, etc) but nothing worked. Here's my problem:

I have a very simple scene: a box with 4 spherical vray lights. Render it with these settings:






The render looks like this:






It's OK but when I adjust the highlights in PS, instead of nice smooth gradients I get color rings like in a 256-color image:






This is what it looks like in an actual production image:






And here is the whole image for your ref:






This happened with all 4 different renderings in this project. Any ideas? All help deeply appreciated.

[percydaman]

your boosting the image in PS quite alot, to the point its getting clamped in very 'hot' areas. Try raising the overall illumination of the room some before post, or render to a floating point format if you aren't already.

[MoonDoggie]

looks like an 8-bit image to me. Render out as 16-bit color tiffs and see if that doesn't fix it.

-Colin

[edgemedia]

Percy: I'm only clipping the unused highlights:




Colin: Yes indeed, the 16-bit image looks much better but still with some rings (I can almost go with it):





Interestingly, when I clicked on the sRGB button in Vfbuffer, I got a light but beautifully smooth image (!?):





Is it a color space issue? Of what kind? Why haven't I had it before?

[MoonDoggie]

the sRGB button puts an inverse curve to a 2.2 gamma on it. Glad 16-bits was better. Looking at your render settings everything looks fine, no strange color mapping settings. Try without clamping and sub-pixel mapping and let us see.

-Colin

[vlado]

The V-Ray VFB works with the true floating-point renderer output, which is why you get a smooth image. If you were to save to a floating-point format like .exr and edit this in PS, you will not get any problems as well.

Best regards,
Vlado

[edgemedia]

Colin: the 16-bit noclamp is only very slightly better (I think?) than the one w/clamp (will have to check what my reflections look like w/o clamp):





Vlado: yes, the exr looks very smooth, there's a color shift (sRGB?) but it's quite beautiful:





Thank you all for help.