I wasn't sure which forum was the best for this, so please move it if preferred. Polarizing/polarising filters seem to be a popular subject. Would it be worth having an article or a thread to link to? Making it an FAQ-type article could get round a potential problem caused by varying levels of technicality. Heres a suggested list of questions and an outline of response topics for comment. Best, Helen How could a polarizer affect my pictures? Sky, glare/reflections. Which polarizer should I choose circular or linear? Usually circular, sometimes linear may be OK. Availability, cost. Reason for existence of circular. How do I tell the difference between a linear and a circular polarizer if it isnt marked? Forwards and backwards difference. self-reflection forwards and backwards. What is the technical difference between a circular and a linear polarizer? Circular = linear + depolarizer, in that order. Are there different grades of polarizer, and how do they differ? Quality of foil and glass, lamination method, edge sealing, coating. Can I use my polarizing sunglasses? Likely to be linear. Can I make a variable neutral density filter with two polarizers? Linear + circular vs reverse circular + circular. Spectral (colour) errors. Difficulty of manufacturing polarizers that are spectrally neutral. Possibility of correcting in post. What exposure compensation is required for a polarizer? Is it fixed, or does it depend on the angle? At least 1 stop for an ideal polarizer, never less. Usually fixed, but if looking though glass or water, may need a measurement through the filter. How do I determine the best angle to set it at? Look through it. Guidelines. What about very wide angle lenses? Thin polarizers. Variable effect on sky. My camera isnt an SLR and it doesnt have an electronic viewfinder (EVF). How can I use a polarizer? Various devices, note setting. The front of my lens rotates when I focus/zoom. How does that affect the polarizer? Set focus and/or zoom, then rotate polarizer. How can a polarizer be used when copying paintings etc. Use with pola foil over the light sources. Method of setting up when multiple light sources are used. Can I stack a polarizer with another filter? Not recommended. If necessary pola first. If possible skew filters to reduce number of parallel surfaces.