Originally posted by lithos Unless, of course, you have an autofocus camera.
We had several threads about circular versus linear polarizers during the last 6 months and the general conclusion (based on theory and emphasized by real world trials and useage) was, that the AF system has no problem with linear polarizers, too.
There are only a handful of cameras, which experienced exposure metering problems with linear polarizers (Pentax LX, Olympus OM 2, Nikon F3 for example), because there metering cells were placed behind a secondary, semi-transparent mirror, which itself acts as a polarizer.
So using a linear polarizer with the current line of Pentax DSLRs is no problem at all.
Ben