[Lasselakan]

Hi,
I'm setting up a physically accurate material studio in MAX 2009 and have an exposure issue with HDRI. Renderings at certain exposure come out far more underexposed than expected.

I've created my own HDRI from different exposure photos of a chrome sphere, and merged the RAW-files into an HDR using CS3. I've then added the HDRI to skylight map-slot and environment map-slot in MAX. (I use "Environment Probe/Chrome Ball") Nothing else is in the scene except for a sphere with a chrome material and a camera in position to match the real-world setup.

I activate the "mr Photographic Exposure Control" and set the parameters to match the ones from one of the RAW photos, and when I hit render I expect my rendering to come out more or less similar to that very RAW photo. But it's far too underexposed. The way I've found to render really accurate exposures is to get an exposure of the HDR in CS3 ("View" -> "32-bit Preview Options") and then set the EV parameter in "mr Photographic Exposure Control" to the same BUT negative value. I'm not comfortable with that solution though since it could be unaccurate.

Could someone please help me! I've tried the same setup in VRay where renderings come out identically to the photo, when setting up the VRay Camera as the real-world camera. Just perfect result. How can I achieve this i mentalray?

/Lars