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  1. #1
    3 Star Lounger
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    I have two questions:

    I am noticing what look like water spots on some of my pictures, namely those pictures with a lot of sky in them. The spots look like defects on the lens cover or dirt, but thereís nothing there. Whatís causing these?

    I put a polarizing filter on my camera when shooting under direct sunlight and my digital pictures are all coming out too dark and have to be significantly lightened in PSE. What should I do differently? The polarizing filter did wonders back when I used film.

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    Gold Lounger Roderunner's Avatar
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    Scott, I find this very effective. Find It Here
    O wad some Power the giftie gie us, to see oursels as ithers see us!

  3. #3
    Super Moderator jscher2000's Avatar
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    Quote Originally Posted by Scott Cox View Post
    I am noticing what look like water spots on some of my pictures, namely those pictures with a lot of sky in them. The spots look like defects on the lens cover or dirt, but there’s nothing there. What’s causing these?
    If the "spots" are always in the same position regardless of the light, dust is the most likely culprit. If you have an interchangeable lens camera, dust on the sensor or anti-aliasing filter is a possibility. (Be very cautious in cleaning; just use a plain air squeeze bulb first, not canned air, brushes, or moist wipes.) For fixed lens cameras, sometimes dust creeps into the lens.

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    Super Moderator jscher2000's Avatar
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    Quote Originally Posted by Scott Cox View Post
    I put a polarizing filter on my camera when shooting under direct sunlight and my digital pictures are all coming out too dark and have to be significantly lightened in PSE. What should I do differently? The polarizing filter did wonders back when I used film.
    Most cameras calculate exposure through the lens, so your aperture and/or shutter speed should be adjusted to account for the reduced light. What camera do you have?

    If you dialed down the exposure (e.g., using the EV setting) for regular photos, perhaps it is too low with the filter attached?

  5. #5
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    1. They're only visible on pictures with lotsa sky. (Occasionally water.) They're clearly not dirt nor any lens issue I can identify.

    2. I've been shooting for 25 years, but I'm newer with a digital camera (3 years). I have a Canon EOS 30D. My film pictures with a polarizer turned out well. When used with my digital, it needs to be lightened in PSE about 50%. I never had to compensate with pictures shot that way with my Canon A-1; the camera did that for me. The EOS 30D does not respond the same way. I'm puzzled as to what to do. I shoot in shutter priority. I'm not sure why my digital "sees" the light polarization differently than my film camera did.

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    Super Moderator jscher2000's Avatar
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    Quote Originally Posted by Scott Cox View Post
    1. They're only visible on pictures with lotsa sky. (Occasionally water.) They're clearly not dirt nor any lens issue I can identify.
    Another test is to photograph a sheet of white paper and look for any anomalies. Exaggerating contrast on the image in PSE may help with that.

    Quote Originally Posted by Scott Cox View Post
    I shoot in shutter priority. I'm not sure why my digital "sees" the light polarization differently than my film camera did.
    Does the camera give you an underexposure warning when using the polarizer? For example, flashing the aperture in the viewfinder?

    I've read something about circular vs. linear polarizers for digital vs. film cameras, but haven't paid close enough attention to know whether that might be an issue.

  7. #7
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    jscher2000: Thanks for the input. I'll try the sheet of paper. My quick research indicates, "A circular polarizer is really two filters on top of one another in a single ring......You donít need to know the technical stuff, though, to use a polarizer. If your camera has through the lens metering and/or autofocus, as almost all do today, you will need a circular polarizer. (http://www.digicamera.com/features/f...mer/index.html). Thus, I have a circular polarizer, so I'm using the right kind. So why are my pictures so dark? I don't see any warnings in the viewfinder. There's plenty of light or I wouldn't use the filter. Still puzzled.

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    I shot the sheet of paper as suggested and it had no spots on it. To be clear, there are many spots on the sky pictures, not just one or two. And, they're very circular leading me to think they're somehow not coming in naturally.

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    Super Moderator jscher2000's Avatar
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    Quote Originally Posted by wsc3 View Post
    To be clear, there are many spots on the sky pictures, not just one or two. And, they're very circular leading me to think they're somehow not coming in naturally.
    Can you post a sample or two? You can crop just the sky part to save on bytes. It might be useful to compare with and without filters.

  10. #10
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    Here's an example of what I'm talking about, attached.[attachment=90007:IMG_6392.JPG]
    Attached Images Attached Images

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    Super Moderator jscher2000's Avatar
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    Wow, way more spots than I imagined. And big, too. Was that with or without the filter? It seems a bit dark, so I'm guessing "with." Do you get the same results without the filter? I wonder if the filter got damaged somehow: I think polarizers are a laminate (sandwich) that could come apart over time.

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    Isn't there a lot of spots? This was shot with a polarizer filter. (I did have the light meter set in this picture under by 1 2/3 stops by accident. I discovered that later. Hence the darkness.) I guess it's possible the filter is bad. You know, I'm not sure if I get the spots w/o the polarizer. Hmm. I'll check that out.

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    I don't see anything on the polarizer that I can detect. Could it be that the coating has gone bad or something? It's pretty old.

  14. #14
    Super Moderator jscher2000's Avatar
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    Quote Originally Posted by wsc3 View Post
    I don't see anything on the polarizer that I can detect. Could it be that the coating has gone bad or something? It's pretty old.
    You might try a photography forum like dpReview.com for advice on filter issues. Some photographers probably visit here, too, but this particular board has light traffic.

  15. #15
    Bronze Lounger IanWilson's Avatar
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    Quote Originally Posted by wsc3 View Post
    Isn't there a lot of spots?**This was shot with a polarizer filter.**(I did have the light meter set in this picture under by 1 2/3 stops by accident.**I discovered that later. Hence the darkness.)**I guess it's possible the filter is bad.**You know, I'm not sure if I get the spots w/o the polarizer.**Hmm.**I'll check that out.
    So did you find out whether you get the spots without the polarizer?


    Ian


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