We shoot most of our own HDRIs using Kodak Neutral Density filters and custom scripts to control F-stops and shutter speeds. We found the ND filters were neccesary to capture the full range of the sun intensity for nice crisp shadows when using them with IBL, even when shooting at f22 & 1/8000s.
Im curious how those of you out there using this technique are color correcting the HDRI’s back to account for the ND filter which tints everything a piss yellow/brown. Currently we are “eyeballing it” with non ND filter reference photography but are looking for a more technically correct way of doing this. I had exchanged emails with some people on Paul Debevic’s HDRShop team a while back who said this would be intergrated into future versions of the software thorugh some color matrix math operators (or something like that) but development on that seems to have stalled. Any ideas?
EDIT: The following link is a paper that discusses this technique, including the Neutral Density filter issue. Unfortunalty they don’t go into how they corrected for this in a way which that is very understandable (to me atleast)
www.ict.usc.edu/publications/stumpfel-directhdr-afrigraph.pdf