Frotog - cc filters aren't even mfg to those tolerances. You're dreaming. You'd be far outside the range of a what a good colorhead can do anyway. A push of a button and I can go between presets. Plus you'd be putting something in the lightpath not really designed for over-the-lens use. Lighting gels are not made to the same standards as optical gels, which would cost a small fortune in anything large enough to burn with, and would still degrade the image slightly.