IMHO, isn't this really more an issue of ensuring that film from different cameras with different lenses all looked the same when edited together? In that case small differences (1/8th, maybe even 1/16th of a stop on color film) could make a difference in how the 'print' looked. We're not going to see a 1/8th stop difference in light transmission from frame to frame or sheet to sheet just because we changed lenses. I am certain that there are folks out there who calibrate their exposure and development (N-2 to N+4) for each lens; that would certainly zero out any differences. And if I had a lens that I consistently had underexposure problems with, I'd certainly figure out how far off it was and dial in that compensation. But few of us are anymore shooting cine film from multiple cameras and lenses that has to be edited together to create a single negative (without benefit of conversion to digital) to be used for production of reels to go to the theaters. Bob Younger