75mm w/ polarizer?

[Casey]

Hi Folks,

I've a simple question. I know that with extreme wide angle lenses I'll get banding in the skies if I use a polarizer, but will I also get banding with a 75mm lens? Does anyone out there successfully use a polarizer with a 75mm lens? If so, do you use, say, one of the slim polarizing filters that are offered by various brands? If not, what do you use, and when do you use it?

Thanks,
Casey

[Brian Vuillemenot]

It depends on the angle of your camera towards the sun. If you are at a right angle to the sun, it is possible to get uneven polarization. This is most noticable with blue skies that are darker on one side of the photograph that the other. All lenses have this effect, but the wider the angle of view, the more likely it will be apparent. When using a polarizer with a wide angle lens, it is important to check on the ground glass if this is occuring.

[Alan Davenport]

Assuming that you are using it on 4x5 film, a 75mm lens is an extreme wide angle. Depending on which conversion factor you prefer, it would be equivalent to something like 20mm to 24mm on a 35mm camera.

I think it's safe to assume that you'll get uneven sky effect using a polarizer with that lens. This is not to say the results will necessarily be bad. Try it, what have you got to lose? Even large film is the cheapest part of the trip...

[Patrik Roseen]

Can anyone please explain what causes this 'banding'...is it due to any fault in the polarizer or is this simply what the sky looks like when the 'haze' is removed looked through a wide angle lens.
And is there any difference if using linear or circular polarizer?

[Bob Salomon]

Can anyone please explain what causes this 'banding'...is it due to any fault in the polarizer or is this simply what the sky looks like when the 'haze' is removed looked through a wide angle lens.
And is there any difference if using linear or circular polarizer?

The banding occurs because parts of the sky are polarized naturally and when those areas are included in a scene that includes areas that are not naturally polarized you see those polarized areas as dark bands.

This only occurs with very wide lenses with a polarizer.

[Alan Davenport]

To expand on Bob's reply: the amount of polarization in the sky is primarily dependent on the angle from the sun. You get the maximum amount of polarization from the area of sky at 90 degrees to the sun, and virtually no polarization looking toward or directly away from the sun. Wide angle lenses can image the sky all the way from maximum polarization to none, so the effect varies across the image according to how much polarization is in that part of the sky.