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Old Oct 15, 2006, 4:08 PM   #1
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I have a Maxxum 7D and I am having a problem when using my circular polarizing filter. I use the polarizer to darken the sky and bring out the clouds and colors. In the viewfinder, when I take the picture,it looks fine; just as I would expect. The actual image producedlooksvery different and not ok. In the picture, the sky gets darker and much bluer as you move up away from the horizon. It becomes this unreal shade of blue. Has anybody else seen this problem and is there a fix other than not using a polarizer ?
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Old Oct 17, 2006, 10:25 PM   #2
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i wrote of this same problem i had with a 5D using a circular polarizer.

i used it excessively this summer in St. Lucia, hoping i would get the type of pics i got when using film, with the extra zaaz. but instead all i got was dissapointment a about 300 pics that looked dark and muddy, with contrast between the clouds and sky like a little childs colour painting,

i got a responce from one person about using digital circular polarizing filters made by hoya, but after seeing that price, i would hate to buy it and it ends up getting the same sh*&%^^%$& itty reproduction

but if you buy one please let me know how it turned out:?
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Old Oct 18, 2006, 3:02 AM   #3
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Could you post some picts showing your problem? I have used circular polarizer with my 5D and have no any problem.
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Old Oct 18, 2006, 12:24 PM   #4
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I'm a little confused as well. I use a thin circular polarizer with my 7D with no problens. Yes, it does darken and saturate the sky, but that is expected with a polarizer, and it is within acceptable limits when used on my camera.
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Old Oct 19, 2006, 8:38 AM   #5
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As already mentioned, a Polarizer does tend to bring out the blue in the sky, and it can look a bit odd. Try playing with your White Balance settings (i.e., try custom) and see if that helps out.

Another thing a Polarizer will tend to do is make any vignetting (darker corners) more obvious.

Many lenses have darker corners (vignetting), especially on their wide end at wider apertures (smaller f/stop numbers). This vignetting is more obvious with a Polarizer. Some filters can actually cause a bit of vignetting, too. Sometimes, using a step up ring with a larger than default filter size can help that part out (as can using a thinner filter). But, if it's the lens causing it, you'd need to shoot at longer focal lengths and/or smaller apertures (higher f/stop numbers) to minimize it.



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Old Oct 19, 2006, 12:08 PM   #6
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I'm using the 18-200mm lens at 18 mm.Now that I look at the pictures it could very well be vignetting. Attached is a picture that I just took at Fort Mchenry
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Old Oct 19, 2006, 5:39 PM   #7
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your picture looks great!, Of course the sky is darker on the upper side, but it is what polarizar is supposed to do.
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Old Oct 21, 2006, 12:08 AM   #8
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Looks like a perfectly calculated averaged exposure. Maybe could use +1/2-3/3 f stop exposure...considering that the cannons and cannonballs are "blackish".

We must always remember the basics of exposure. All light meters work on the assumption that the measured subject is of average (18% reflectance or a value of 82% BLACK [ Dk Gray] light vaue (lightness/darkness).

As the subject varies from average...we must adjust exposure accordingly.

Only a incedent light meter can be used for critical exposure determination. It is what is always used to shoot million dollar movies/videos.

Reflected light readings only work as well as the photographer works with it, knowing how it works. Ansel Adams zone system for example.

Oh yes, color (hue) doesn'e even figure into it as far as the theory goes...BUT different types of light sensors don't see hue the same so, it does matter.

So then, exposure is an art as much as a science,,,at least in practice, for most of us.

JohnJuan


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Old Oct 21, 2006, 12:11 AM   #9
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Oops pls forgive typo...that's +1/2 -2/3 f stop. JohnJuan
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Old Oct 21, 2006, 3:20 PM   #10
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I'm just surprised that the darkening isn't more uniform across the sky. That is the way it looks in the viewfinder and that is the way it worked with film. On the other hand I only used a 50mm lenswith my Nikon N80 and maybe I didn't see enough of the sky for this effect to show up. Attached is another picture taken in a field near my house. It was taken with the lens at 18mm.
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