Irix Revo UV Protector Filter

The Irix Revo UV Protector is the filter that lives on the lens: tempered glass carrying eighteen coating layers, sitting in a frame only 3.7 mm thick so it will not vignette on a wide angle. Light transmission measures 98.9 percent across 420 to 750 nm, which is close enough to no filter at all that there is no reason to take it off.

The coating stack is doing more than cutting reflections. It is hydrophobic and oil resistant, so rain beads and fingerprints wipe off rather than smear, and it is scratch resistant on top of tempered glass that is there to take an impact the front element should not. The front is threaded, so a hood or a second filter still screws on. Twelve thread sizes from 37 mm to 82 mm.