When I use a circular polarizer in the EF 100-300/5.6L the viewfinder looses sharpness and the image seem to be out of focus. I don't know the result after taking the picture because I haven't done any yet with the polarizer, but I suppose that it won't be sharp enough.

When using AF without the polarizer, the result is excellent. Once it is focused, if I fit the circular polarizer without moving the focus...the image is out of focus! Like you know, in this lens, the front turns or rounds (my english...) when you are focusing. My question is if I should use a linear polarizer insted of circular (I don't know the difference actually).

Really mixed up. Peio Ezkurra - Basque Country.

-- Peio Ezkurra (peio_e@hotmail.com), February 13, 2002

Answers

It sounds like you have a defective polarizer.

The filters section of photo.net (http://www.photo.net/photo/filters) covers things like the difference between linear and circular polarizers.

-- Steve Dunn (steved@ussinc.com), February 13, 2002.

What brand polarizer is it? You didn't buy a Cokin did you?

Using polarizers on that particular lens can be a pain since the front lens elements rotate and you have to readjust the polarizer constantly. Even so, this sounds like a bad filter.

-- Lee (Leemarthakiri@sport.rr.com), February 13, 2002.