No Glass Reflections Against White Background?

[leejk]

Hello,

I have a problem that I can't figure out. If I use a white environment background I get no reflections in the glass, yet the reflections are present in the VRayReflection render element. Or if I use a background image in the environment slot, there are no reflections shown. But if I set the background color to a darker color, the reflections show as expected. I am using a dome light with default settings and a basic glass material. See attached example images.

I have checked the geometry and everything else I can imagine. What could be causing this problem?

thx

[leejk]

And just now figured this out . For whatever reason, I changed the exposure setting from 8.0 to 8.5 on the Physical Camera and that solved it. Maybe someone has an explanation on why that helped.

[kosso_olli]

Well, if your background is white, the color value is 255/255/255. That is maximum intensity. No matter what you add to it (reflections), it can not be shown, because the values already are at maximum. Darkening the background as you did will leave room for the reflections to contribute to the final RGB value.
By lowering the exposure, you probably made sure that the value for the background is below 255/255/255.

[leejk]

Yes, that sounds right. The background color was 240. However my desire was to use this in a comp and therefore was needing the background color to be black, but that lowered the overall scene lighting. So was going to try and make it work with white. Then I found this informative post about how the dome light works in detail. After realizing that my dome light was "leaking", fixed that and changed background color to black and EV on camera back to 8.0. Now everything is working as expected.