View Full Version : Exposure factor of B&W PL?

6-Mar-2001, 00:35
Recently I got a B&W PL, but I could not find anything about exposure factor on the box, and they didn't print it on the ring. Anybody can get me tips? Thank you.

pat krentz
6-Mar-2001, 01:46
What is a B&W PL? Pat

Robert A. Zeichner
6-Mar-2001, 08:19
I'm going to guess this is a polarizer. If so, you might start at 1-2/ 3 to 2 stops. I suppose you could also meter through it at a flat target like a grey card.

Pete Andrews
6-Mar-2001, 13:01
I expect it's a B&W manufactured linear polariser you're referring to.I'd go with the above, 1.5 to 2 stops, but it really depends on how much polarised light is reflecting from the subject. Stick it over your meter or take a TTL reading.

Brian Ellis
6-Mar-2001, 18:01
Pete's statement that the factor depends on the amount of polarized light sounds logical but I believe it is incorrect. The factor is the same regardless of the amount of polarized light. See, e.g., Adams, "The Camera," p. 169. "The filter factor for a polarizer is usually 2.5; it is not correct to assume that the exposure factor increases as the amount of polarization increases, since this would result in overexposure of the non-polarized areas."

Erik Gould
6-Mar-2001, 21:36
I use a polarizer quite a bit and I allow 2.5 stops for it. I shoot 4x5 transparencies and that factor is right most always. you can meter through it if you want to be sure.