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12-23-2009, 08:30 PM   #1
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Problem shooting with polarizer

Always wanted a nice polarizer with my SLR's and finally got one for my K-x. It is a decent B&H circular (multicoated), got a good deal on it! Will be taking a lot of photos in the coastal areas and bright sunny spots, and thought this would help, however...

Pardon my ignorance, but here are the problems:

1. Several images I took seem quite dark (all taken with AF and "Auto" shooting mode). What is the recommended exposure adjustment when shooting with this filter? Shouldn't the light metering sensor be doing it's job regardless?

2. Rotating the filter does not seem to make any difference in the amount of blocked reflected light. Perhaps, I selected a wrong subject for shooting (some concrete and water surface), but I was expecting effect similar to what you get when you wear good polarizing sunglasses. My understanding is that there should be significant difference at 0 and 90 degrees?

Very disappointed so far, feel like I wasted my money. Am I doing something wrong?

12-23-2009, 08:35 PM   #2
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With an SLR which meters through the lens, you shouldn't have to make any exposure adjustment - the meter should do it by itself. Make sure you were in the right mode ie Av, Tv or Auto and that no exposure compensation was being added. The polarizer works best in sunlight - not as well with diffuse, cloudy light. You should see sunlight reflections on water practically disappear when the polarizer is 90 degrees offset from the polarity of the light. The sky will darken also when you hit the sweet angle. I don't know what the lighting conditions were but I suspect it was diffuse.
12-23-2009, 11:32 PM   #3
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As I indicated above, it was auto mode with no additional adjustments.

The shooting conditions - early morning, sun low reflecting on the water surface and some concrete. The filter pretty much obliterated shadows making them very dark and the reflected light did not seem too different from the pics taken w/o filter.

What puzzles me most is that I expected to see some difference by rotating the filter but I have not been able to see any. Is that normal?

I would have to try it under different conditions, especially coastal photography before I decide to return it or sell it. Still disappointed...
12-24-2009, 08:25 AM   #4
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A polarizer's effect is most noticeable when the light is shining perpendicular to the lens' axis. That is, when the light is coming from one side or the other, or straight down.

If the light is directly behind you, for example, the effect is minimal.

This can lead to one drawback of a polarizer. While the polarizer usually darkens the blue sky quite a bit, if you're shooting with a very wide lens, you can sometimes see a dramatic variation in the effect across the sky. This is because at one side, the light is perpendicular, while at the other side, it is not.

12-24-2009, 09:11 AM   #5
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There is a chance the filter element was installed backwards during assembly. You can tell if this is the case by looking throught the filter at an LCD screen as you turn the filter. The filter will go dark while turning as you look through it in the correct direction.

Reflections from water are most polarized at an angle of about 33 degrees to the water surface (ie. a shallow angle).

Dave
12-24-2009, 12:31 PM   #6
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Try again with a good polarizing filter. It should make a huge difference.

I bought the most expensive BH filter and hated it. Mine was not even color neutral and cut off in the blue wavelengths too early. A European website (sorry I donīt remember which one) did tests on the BH UV filter and found the same problem. Needless to say, I sold mine as fast as I could.

Now I use a Hoya Super Multi-Coated and Hoya HD Polarizer and they perform admirably.

- Itai
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12-24-2009, 02:50 PM   #7
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Are you metering off the *sky,* perchance? Or directly off sunlit concrete or shining waters, as you imply? (Are the dark images ones which have something really bright in the middle of the frame?)

Often when folks first get a polarizer, they of course want to photograph these things, you see.

Even with a polarizer, that will cause automatic exposure to want to treat bright sky (or whatever) as though it were a more ordinary subject. (ie, the camera will think it's a normal subject which it must reduce exposure to get you your photo.)

It's probably not anything you're doing 'wrong,' so much as things you're not doing.

There are several ways to effect some compensation for this kind of thing: probably the simplest, if you're using automation, is to point the camera a little away from the source of brightness, and use 'ae-L' to hold that reading while you frame the shot you'd like.

The camera's automation will be very clever, but it's not a mind-reader. It doesn't know that the very bright spots aren't supposed to look something like a human face under ordinary sun, for instance, (it only knows that there are bright areas and dark areas, in the case of 'matrix metering.' In the case of 'average' metering, it will simply take an overall reading biased toward the center.) Polarizers can help knock these effects down a notch, but they aren't that strong or precise: Concrete is a very reflective material, and omnidirectionally-so: unlike glass or reasonably-still water, it reflects at all kinds of angles, which polarizers simply can't cover all of.


(They can cut out the strongest: many of those which most directly-reflect the Sun, but not all. You still have a very high 'albedo' subject. It will *still* be brighter than your camera will assume your subject is supposed to look. Your eyes and brain are more 'automated' than the smartest camera. Part of photography, is actually learning to see the light more *simply* than you take for granted just looking at stuff. )

Anyway, in short, this is part of why we have all kinds of manual and exposure-managing features, still.


For now, try pointing your camera somewhere without too much exceptionally-bright stuff in it, but under the same light, hold that reading, and reframe. You may start to get a sense of what's going on. (Also, if it's too dark, try using that +/- button to *give it more light.* I suspect with what you're describing, you'll want it to be +2 or +3 stops.)

Last edited by Ratmagiclady; 12-24-2009 at 02:58 PM.
12-24-2009, 04:37 PM   #8
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If you just want to check if the polarizer is actually doing any difference, you don't even have to take an actual photo.
Find an object with a flat surface that is reflective of light (even indoors)..like find a photo on a frame or painting on a frame with glass in your house and look for an angle where you can't see the picture inside the glass or just part of the picture inside the glass because of reflected light on the frame.
Try to view with the camera on that angle then slowly rotate the polarizer.
You will be able to see that the reflected light off the glass on the frame will disappear and you will be able to see the picture underneath it.
If you like, take a photo with the reflected light and with the rotated polarizer too cutting off the reflected light.

12-24-2009, 04:46 PM   #9
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Here is an example of what I was talking about.
I was at an angle of the photo frame on the wall and the light from the side was reflecting off the photo.
Upon using the polarizing filter, I was able to cut the reflection off and get the whole scene without any annoying glare.
Photo 1 is with reflection.
Photo 2 is with polarizer turned to cut glare off photo on the wall.
Sorry, didn't correct WB.
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12-26-2009, 02:06 AM   #10
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Thank you. I will have to do more testing under different conditions, but I did look through the filter directly (without being mounted on the lens). It performs as expected - rotating polarizes the light.

It seems that under certain light conditions, some exposure compensation will be needed to avoid the problem I originally described.
12-26-2009, 04:18 PM   #11
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Good luck and happy shooting.
We can only learn from experience.
I should say "it is better to learn" from experience.
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