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  1. #1

    Join Date
    May 2014
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    Using Behind the Lens Filters

    I recently acquired a Calumet/Xenophone behind-the-filter holder for my 8x10. It fits a 3" square gel filter. I have a 14.75" Caltar lens in an Ilex #5 shutter. Not a lot of documentation about mounting these filter holders. I've read everything from Velcro to double side tape to clipping it on. And I notice the three clips have screws but I have no idea what they're for. I was able to just use the tension of the three clips and fit it around the rear barrel of the lens inside the camera. It stays in there but doesn't feel quite right.

    Also, having a filter inside the camera isn't really conducive to quick changes or adjustments. I do studio portrait work, and if I'm doing a lot of black and white, it can stay in there... I guess. Do people using these typically frame and focus through the filter? Mine is a Wratten #58 gel filter. Everything is green and not as bright in the ground glass.

    Thank you.

  2. #2

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    Re: Using Behind the Lens Filters

    You must focus through the filter since, besides other adverse effects on the image, it will also create a focus shift. Filters belong in front of the lens unless they are part of the lens design.

  3. #3

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    Re: Using Behind the Lens Filters

    Quote Originally Posted by Bob Salomon View Post
    You must focus through the filter since, besides other adverse effects on the image, it will also create a focus shift. Filters belong in front of the lens unless they are part of the lens design.
    Gell filters are so thin; would the focus shift involved really be that much of a problem?

  4. #4

    Re: Using Behind the Lens Filters

    Quote Originally Posted by neil poulsen View Post
    Gell filters are so thin; would the focus shift involved really be that much of a problem?
    I very much doubt it.

  5. #5

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    Re: Using Behind the Lens Filters

    Quote Originally Posted by neil poulsen View Post
    Gell filters are so thin; would the focus shift involved really be that much of a problem?
    I've used gel filters behind the lens on my 8x10 for 30+ years and I've never noticed any issue with focus shift. Can't say I've tested with/without side-by-side, but I would have had I noticed anything unexpected with my negs.

  6. #6

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    Re: Using Behind the Lens Filters

    Quote Originally Posted by Alan9940 View Post
    I've used gel filters behind the lens on my 8x10 for 30+ years and I've never noticed any issue with focus shift. Can't say I've tested with/without side-by-side, but I would have had I noticed anything unexpected with my negs.
    With a thin gel you won't notice a focus shift, because the shift it is said to be 1/3 of the filter thickness. But if you place a thicker filter (like a Pol) behind the lens then you should be able notice the shift, like bob stated.

  7. #7

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    Re: Using Behind the Lens Filters

    Quote Originally Posted by Pere Casals View Post
    With a thin gel you won't notice a focus shift, because the shift it is said to be 1/3 of the filter thickness. But if you place a thicker filter (like a Pol) behind the lens then you should be able notice the shift, like bob stated.
    I remember reading one time in a in a Kodak publication that their gel filters caused a shift of 1/2 of the thickness of the gel... Heck, if their gels caused a shift of the full thickness of their gel filters, I seriously any of us would notice it.

  8. #8
    Tin Can's Avatar
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    Dec 2011
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    Re: Using Behind the Lens Filters

    https://www.bhphotovideo.com/c/produ...pter_Ring.html

    https://www.keh.com/shop/large-forma...der-27551.html

    Rare

    I once bought a lens on a Sinar board with a DIY setup, which I removed,

  9. #9

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    Apr 2013
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    Re: Using Behind the Lens Filters

    I have the filter behind my lens quite often, and have never had an issue while focusing through the filter

  10. #10

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    Re: Using Behind the Lens Filters

    The Xenophon BTL filter holder sold by Calumet was designed for the Schneider 121/8 (or 120/8) Super-Angulon lens. Gaffer tape has held mine in place for over 20 years. Not, perhaps, the most elegant solution, but few people have ever seen inside any of my cameras.
    When using that lens I choose the filter first (Kodak Wratten gels), install it, and then focus. Never a resolution issue yet.

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