Reflection filter, and reflection raw , when multiplied do not match up with the reflection pass. This doesn’t appear to be a problem with pre\unpremultiplication as the differences show up inside a single mesh itself when one part occludes another, and not at the alpha edges.
We’ve found that the base passes all add back up to the original beauty perfectly, but if we try a larger comp tree with the Filter passes (any of them) multed against the raw there are internal edging artifacts and a different final result.
Do you use any color mapping? Elements should be in linear color space before performing any operations on them.
Anyways, there are some known issues with the raw elements due to the way they are calculated. Currently a work-around for this is to calculate the raw elements yourself from the regular element and its filter (f.e. reflection=raw_reflection*reflection_filter => raw_reflection=reflection/reflection_filter). This is going to be fixed in V-Ray as well.