on 1/16/05 9:59 PM, Dr. Elliot Puritz at drpuritz@xxxxxxxxxxxxx wrote: Might I ask a quick question regarding polarizers and two of the R lenses? With reference to both the 21-35 Asph, and the 28-70 zoom lenses ( not the uncommon Asph version ), is there any magic to using the polarizers? Does one simply obtain a circular polarizer of the correct size, and screw it in? Sorry for asking what must appear to be a very simple question. Elliot There is an article in Popular Photography, Sept 2002, probably available on the net, which advises if you own an slr with through the lens metering, you'll probably need a circular. Also, with the 21, it might be best to get the thin mount to avoid vignetting. I got a thin mount from B&H and it works fine. Jack Sikes