Polarizer problem - DPChallenge Forums

Nikon AF-S DX Zoom-Nikkor 18-70mm f/3.5-4.5G IF-ED

05/06/2007 07:51:22 PM · #1

I have been using a B+W 77mm slim C-POL circular polarizing filter on my Canon 10-22mm and Canon 17-40mm L lenses. But when I do, there has been a strange dark, discolored section in the top center of the shot. Here is an example:

The discoloration is always the same shape and in the same space. So I have two questions:

1. Has anyone else seen this kind of problem? If so, do you know what causes it and if there is a way to fix it? (Okay, this might add up to more than 2 questions.)

2. Assuming that this is a problem with the filter that can't be fixed, I'd like to buy a replacement. I like the descriptions of the Calumet multi-coated SMC filter and the Sigma EX DG specially designed for wide-angle lenses. Can anyone recommend either of these filters or perhaps a different one?

Edit to add that I used a Kenko 72mm polarizer on a different lens the same day, and those shots turned out perfectly fine.

Thanks!

Message edited by author 2007-05-06 19:52:45.

Tycho

Nikon D70

05/06/2007 08:00:30 PM · #2

Uneven polarization is normal when you put a polarizer on a super wide lens. Some people like that effect, some don't.

Nikon AF-S DX NIKKOR 18-200mm f/3.5-5.6G ED VR II

05/06/2007 08:47:46 PM · #3

Yes, but some polarizers are designed to prevent this problem, which is what I'd like to find. Anyone have good experiences using polarizers on a wide-angle lens without this effect?

zardoz

Nikon D200

05/06/2007 09:03:55 PM · #4

The effect you are seeing is the normal action of a polarizing filter. Maximum polarization of sunlight occurs at ninety degrees to the sun. Looking straight at or away from the sun the light is relatively unpolarized. A wide angle lens will see enough of the sky for this uneven polarization to become visible. You wont notice it with any longer lens.

Message edited by author 2007-05-06 21:04:44.

kirbic

Canon EOS R5

Canon RF 24-70mm f/2.8 L IS

05/06/2007 09:06:52 PM · #5

As zardoz posted, with a very wide angle lens, the effect is unavoidable, since the actual amount of polarization of the sky varies. No polarizer can get around this. The one you have is a very good one, BTW.

zardoz

Nikon D200

Nikon AF-S DX NIKKOR 18-200mm f/3.5-5.6G ED VR II

05/06/2007 09:08:31 PM · #6

Originally posted by PhilipDyer:

Yes, but some polarizers are designed to prevent this problem, which is what I'd like to find. Anyone have good experiences using polarizers on a wide-angle lens without this effect?

I've never heard of such a thing.
The colour cast in your example picture is a little off, the darkened band is normal however. I have seen some cheap polarizers that did introduce a colour cast.

Nikon AF-S DX NIKKOR 18-200mm f/3.5-5.6G ED VR II

05/06/2007 10:03:46 PM · #7

The link to that Sigma polarizer says that it was designed specifically for wide-angle lenses, though it specifically mentions that its main benefit is to eliminate vignetting. If what you're saying is true, then it seems like there is never any reason to use a polarizer with a wide-angle lens, unless I happen to like that parabolic color banding it produces.

zardoz

Nikon D200

05/06/2007 10:15:24 PM · #8

Originally posted by PhilipDyer:

That about sums it up :-) The only thing special about polarizers made for wide-angles is that they are very thin to avoid vignetting. I wouldn't go so far as to say they are never of use for wide-angles but the banding is something that you have to keep in mind.