Exposure factor of B&W PL?

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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.

-- max (sf192324@sina.com), March 05, 2001


What is a B&W PL? Pat

-- pat krentz (patwandakrentz@aol.com), March 06, 2001.

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.

-- Robert A. Zeichner (info@razeichner.com), March 06, 2001.

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.

-- Pete Andrews (p.l.andrews@bham.ac.uk), March 06, 2001.

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."

-- Brian Ellis (bellis60@earthlink.net), March 06, 2001.

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.

-- Erik Gould (egould@risd.edu), March 06, 2001.

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