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Thread: Lens flair caused by filter?

  1. #1

    Lens flair caused by filter?

    The other day I got to wondering if I could make panoramic images by using my 90 mm Super Angulon f8 on my 8x10 and getting a 4” x 9” picture. The image circle is listed at 216 mm ( I hoped to squeak out a smidge more) and it was one of those things that sounded like a good idea at the time.

    About everything went wrong that could.

    I made a ½ dark slide so I could make two images on 8x10 but then found when I put that lens on an 8x10 camera, the bellows were completely compressed, so I had no rise. I would have to waste a full sheet of film.

    I planed on creating a gradient mask in Photoshop and printing it on transparent material with an ink jet printer to use instead of a center filter when contact printing. I then found out that transparent sheets for ink jet printers sell for almost as much as film and are 50 to a box!

    Then I put a fairly thick name brand screw on red filter on the front of the lens and made the mistake of allowing the sun’s disk filtered through heavy overcast to be in the edge of scene.

    When I processed the negative I had a circular band of flair about ¾” wide from about the 1:00 to the 4:00 position toward the edge of the negative on the opposite side of the sun’s disk.

    It started close enough to the center of the negative that it would have been on a 4x5. I have used this lens many times and never had the problem before.

    I decided that this must have been caused by the front and rear surface of the filter?

    I then thought that had I anticipated this, I should have put the filter on the back of the lens.

    Now, Bob Solomon says in the prior post, never put the filter on the back of the lens. Could this be the one exception, or do I have my problem misdiagnosed completely?

  2. #2

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    Lens flair caused by filter?

    No this is no an exception. There really are no exceptions for putting a filter on the back of a lens (save perhaps a gel).

    However it sounds like the filter you used was either not coated or was not properly multi-coated on both sides. Without effective MC on both sides flare is very probable on each glass to air surface. That would include glass to air surfaces in back as well as in front of a lens.

  3. #3

    Lens flair caused by filter?

    Howdy Neal... I am surprised that you were adventurous enough, and went through all the planning and construction in your experiement... Now you are afraid to try rearmounting a filter just because "Bob said so"???

    I have used filters on the back of my 10"wf Ektar with success. Bob is correct about watching for focus shift... and I am sure you make a good effort to keep your filters clean, so why not give it a try???

  4. #4
    tim atherton's Avatar
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    Lens flair caused by filter?

    "No this is no an exception. There really are no exceptions for putting a filter on the back of a lens (save perhaps a gel)."

    what about a lens that has the thread on the back but not one on the front.. :-)
    You'd be amazed how small the demand is for pictures of trees... - Fred Astaire to Audrey Hepburn

    www.photo-muse.blogspot.com blog

  5. #5

    Lens flair caused by filter?

    Two parts:

    Given that the problem was caused by the filter:

    1) Would the problems caused by putting the filter on the rear element be likely to be worse than the flair caused by having it on the front?

    2) Is the problem with lack of multicoating worse with the dark red filter than it would have been with say a light yellow? (I might spring for one first class brand new filter but not a whole set.)

    I will try it again, but first I need a new box of 8x10 Tmax and a shot that gives me simular light conditions and sun position. (Note: I ran accross a paragraph from Ansel Adams that suggested that flair was more likely on overcast days than bright sunshine because the light making up the image was closer in intensity to the flair causing light. He went on to say that the sun need not be in the frame. This may have been the case here.)

    I am supprised that no one has jumped me for not using a shade but I figured that with 100 degrees of coverage, the shade wouldn't have been much more than a black pie plate.

    P.S. This wasn't subtle, my guestimate is that the band of flair was at least a full stop darker (on the negative) than the area around it. I have to print it to scan it, and it didn't seem worth the sheet of paper.

  6. #6

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    Lens flair caused by filter?

    Tim,

    Quite frequently threads on the rear are used for a retaining ring to screw into. Not for a filter.

  7. #7

    Lens flair caused by filter?

    I don’t know what is the big deal of screwing the filter onto the back element (at the rear). It works for me, and dare anyone to show me the difference on the transparency. Of course, one focuses with the filter in place and keeps it clean as well!

    A filter should never be used on the rear element (unless the lens was designed for a rear filter).

    Yes, a lot of things are not designed in a certain way, but we still try to find different ways. That is why we have round wheels among others. Most photographers would wish that a minor image degradation were their only problem :-))

  8. #8
    tim atherton's Avatar
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    Lens flair caused by filter?

    "Tim, Quite frequently threads on the rear are used for a retaining ring to screw into. Not for a filter."

    Oh probably - but if it's the only thread you've got, it's the one you use... and it works just fine.
    You'd be amazed how small the demand is for pictures of trees... - Fred Astaire to Audrey Hepburn

    www.photo-muse.blogspot.com blog

  9. #9
    tim atherton's Avatar
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    Lens flair caused by filter?

    Doesn't HP sell a rear filter system? (who used to do that neat magnetic one that isn't sold anymore? It worked very well - but was, of course, discontinued...)
    You'd be amazed how small the demand is for pictures of trees... - Fred Astaire to Audrey Hepburn

    www.photo-muse.blogspot.com blog

  10. #10

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    Lens flair caused by filter?

    Calumet sells their Zenophon rear filter holder. I use tabs of industrial strength velcro on the backs of my lens boards to hold on the Zenophon. You typically use 3 inch gels with this holder. Works great!

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