Edmunds Optics and Prinz sell linear polarizers of nearly any thread type/combination, as well as unmounted. Probably cheaper than Leica. Perhaps search the Edmunds site http://www.edmundoptics.com/onlinecatalog/browse.cfm?categoryid=166 BR From: CCP4 bulletin board [mailto:[log in to unmask]] On Behalf Of Terje Dokland Sent: Wednesday, January 21, 2009 9:16 AM To: [log in to unmask] Subject: [ccp4bb] Polarizing filter We are looking to buy a polarizing filter for our Leica stereomicroscope that we use to observe crystals. However, I am a little confused about the types of filters that are available from photography stores; specifically there are "linear" and "circular" polarizers. I would guess that what I need is a linear polarizing filter that can rotate, though these are harder to find than the circular polarizers that seem to be more common for general photography. Any advice? Thanks, Terje --- Terje Dokland, PhD Associate Professor Department of Microbiology University of Alabama at Birmingham 845 19th St South, BBRB 311 Birmingham, AL 35294 Tel: (205) 996 4502 Fax: (205) 996 2667 Do. Or do not. There is no try. -- Master Yoda