How is measured BRDF data recorded? Like the MERL BRDF Database.
What kind of equipment is used and what are the key values that need to be recorded?
I know one place this data was used was in the Disney PBR paper.
Section 6 of Microfacet Models for Refraction through Rough Surfaces has a good description of how they did it to validate their own model. That may not be everything needed to build a full database (eg. more automation) but it's an interesting read.