Polarisation Filter

[r.e.]

And, it's easy to determine how a polarizer will render a scene; simply look through it... EZPZ.

This is why I'm not complaining about the 112mm (4.4") polariser that I recently purchased for use with Schneider's Centre Filter IVa, or about my 100mm (4") square polariser. When it comes to holding up a polariser to a scene to work out rotation, big is good

[cowanw]

The density of a single polarizer, circular or linear, does not change as you rotate it. It always passes the same amount of light, regardless of its rotation.

I have read this before and I have been thinking about this recently and wonder how that can be so if the filter blocks light whose waves are in one or other plane.

[Pieter]

B+W states their polarizing filter factor as 2 to 3 (1 to 1.5 stops), not as a single factor. They also suggest not using a focal length less than 28mm in FF 35mm format, for an even effect.

[LabRat]

B+W states their polarizing filter factor as 2 to 3 (1 to 1.5 stops), not as a single factor. They also suggest not using a focal length less than 28mm in FF 35mm format, for an effect.

Unless you want a big, dark "kidney bean" in the blue sky... ;-)

Steve K

[pdmoylan]

B+W states their polarizing filter factor as 2 to 3 (1 to 1.5 stops), not as a single factor. They also suggest not using a focal length less than 28mm in FF 35mm format, for an even effect.

Exactly.

My method though supercilious gave me precision with color transparency film where even being off by 1/3 stop produces a “throw out”. Those who shoot Velvia know.

[xkaes]

B+W ... suggest not using a focal length less than 28mm in FF 35mm format, for an even effect.

That's a very arbitrary focal length to choose, and only applies to a few subject, like some clear blue skies -- some of the time. I've used polarizers with fisheye lenses, with perfect results, thank you very much!

[Greg]

The density of a single polarizer, circular or linear, does not change as you rotate it. It always passes the same amount of light, regardless of its rotation.

I do agree with Bob that the polarizer always passes the same amount of light, but it has been my experience that areas of the image may change by several Zones (usually becoming darker) and this affects how one takes their meter readings and determines one's final exposure. When I was shooting 4x5 Chromes, the only way that I had gotten accurate exposures was to use my Sinar Six meter with the polarizer rotated in its final position. For B&W I just always used the same loss of 1 1/2 stops.

[Alan Klein]

Exactly.

My method though supercilious gave me precision with color transparency film where even being off by 1/3 stop produces a “throw out”. Those who shoot Velvia know.

So how do you meter with a polarizer like B+W that recommends adjustments from 1 to 1 1/2 stops?

[Pieter]

So how do you meter with a polarizer like B+W that recommends adjustments from 1 to 1 1/2 stops?

Through the filter with a reflected light meter. Or with the meter attached to a camera with a TTL meter.

[Pieter]

That's a very arbitrary focal length to choose, and only applies to a few subject, like some clear blue skies -- some of the time. I've used polarizers with fisheye lenses, with perfect results, thank you very much!

How do you use a polarizer to any predictable effect with a fisheye lens? I assume the filter has to go behind the lens. The unevenness of the effect is because the actual sky light is unevenly polarized and becomes more apparent with ultra-wide angle lenses.