After reading this thread several months ago, I started using this method to set the whitepoint of my VRayPhysicalCamera. It worked well. However, since I installed the final release of version 1.5 it doesn’t seem to work.
I was creating a 255,255,255 white box on the floor of my interior scenes. I would then check the pixel information on the pure white area. It is typically shifted off based on the other colors in the scene, or the lighting in the scene. I would use the sampled white RGB information in the custom balance area of the VrayPhysicalCamera. Then I would do the math described in the thread to adjust the ISO. Then I would re-render a patch, and check the whitepoint again. In the past the RGB values returned were always within 1 number of each other. Meaning it would be something like 245,244,245.
Now, since using version 1.5 final, the values after setting the white point are typically 8 points off, and it shifts the color of the scene worse than what it was before I set the whitepoint. Meaning the white the sampled area would be something like 253,245,244.
Anyone else using this method? …or have a different method? …or tell me what I am doing wrong.
It still works flawlessy to the third decimal with both standard lights and sun and sky, here.
Make sure your gamma settings are set to 1.0 in all three spinners.
hmmm… now it seems to be working fine. i am using linear with 1 multiplier for dark and bright multipliers, but burning the gamma in with a 2.2. which i didn’t think would matter, but maybe it did.
however, after testing it in in full linear and having it work fine, i switched back to burning the gamma at 2.2, and it also worked fine.
the problem may have came with the CoolPick plugin. sometimes i have it at what i think is 255,255,255, but the luma slider is pushed over, and i don’t notice. so maybe i was sampling the white to set the white point, but i was sampling off a color that already had a custom balance applied to it.
i thought i had double checked that once before, but maybe i didn’t.
Gamma is basically a multiplier for image brightness, which is able to vary by pixel.
In the case of our 2.2 gamma, the brightest parts will be mostly unaffected, while the darker one will get the higher boost.
Mostly unaffected, though, not entirely unaffected.
Hence they will vary in intensity, if little (comparatively to the dark ones).
Sorry to hijack this topic, but i am sure i am not that far off…
Lele: could u please explain your method in comparison with the new camera exposure in vray final? is your method still actual? or lets say…is it still so big difference using your method? Thank you!