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Old 5th of August 2003 (Tue)   #1
Belmondo
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Default Circular Polarizer on 17-40L

I live in the California desert. Generally, my choices are: take pictures with lots of sand and/or pictures with lots of sky. We don't have that many pretty little flowers to use our macro lenses on. Besides, we have Africanized Killer Bees around here competing for those precious few flowers.

Today I was taking pictures with lots of sky using my 17-40L with a Hoya circular polarizer. Upon reviewing the images, I observed that sky was darkened by the filter as expected, but portions of the sky (particularly in the corners of the image) were much darker than others. Is this a common problem with circular polarizers, or is it an anomoly inflicted on just me?

Is that more pronounced with wide-angle lenses? Is the only solution to use less polarizing effect? If so, is there another way to crank up contrast (besides post-processing)?

Thanks, friends.

By the way, This forum is wonderful. I've learned a great deal.
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Old 5th of August 2003 (Tue)   #2
Barry in Md
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Default Re: Circular Polarizer on 17-40L

It sounds as if the polarizer was vignetting at the widest angle of your zoom. I am assuming that this was noticible when you were at 17mm but not so at 40mm. You can get "thin" filters that reduce/eliminate this effect. I use a Hoya thin with my 16-35 and have no problems.
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Old 5th of August 2003 (Tue)   #3
Belmondo
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Default Re: Circular Polarizer on 17-40L

Thanks for the suggestion. I really don't believe that's the case, however. As I understand vignetting, it's an actual obstruction of the image by the filter ring or some other 'thing.'

This is a gradual darkening of the sky that that begins in roughly the center of the image and increases toward the edge of the image. Interestingly, it alternated between corners, probably as a result of turning the filter while adjusting the zoom (or something).
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Old 6th of August 2003 (Wed)   #4
RGorrill
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Default Re: Circular Polarizer on 17-40L

Hi,

The problem with the darkening problem is the extreme wide-angle lens that is covering a much larger area of the sky than a normal lens or a not-so-wide angle lens. Just the basic facts of polarized life.

Bob
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Old 6th of August 2003 (Wed)   #5
Belmondo
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Default Re: Re: Circular Polarizer on 17-40L

Quote:
rgorrill wrote:
Hi,

The problem with the darkening problem is the extreme wide-angle lens that is covering a much larger area of the sky than a normal lens or a not-so-wide angle lens. Just the basic facts of polarized life.

Bob

I already resigned myself to that fact. I'm mostly relieved that there isn't anything wrong with my camera and/or me. It's also very comforting to know that the sky out here really isn't turning black.
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Old 7th of August 2003 (Thu)   #6
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Default Re: Circular Polarizer on 17-40L

Starts turning black at about 70,000 feet
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