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  1. #1

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    Center filters - WTF? $$$$$$$$$$$$

    I'm in the process of re-outfitting my 4x5 gear for wider angle work. I'm looking at a current 90mm Schneider 5.6 XL, and also a 72mm Schneider 5.6 XL (or possibly a Rodenstock 75mm 4.5 Grandagon N).

    Some questions regarding these ridiculously expensive center filters:

    1) If I'm realistically going to be shooting at f16 or smaller, do I really need these? Even on a 90mm?? Is there that much falloff at working apertures??

    2) In the Rodenstock litterature it says the center filters are optimized for the working aperture (say f16). Ok, what happens if I'm at f22 or smaller? Do you need to remove the filter at smaller apertures than the aperture for which they are "optimized"? Seems to me if falloff decreases as you stop down, at some point falloff is reduced to the point where a center filter would be detrimental, causing the center of the image to be darker than the edges. ?

    3) Are these filters always necessary or only when movements are involved (eg significant front rise typically required in architectural work)?

    Experiences and thoughts welcome.

    Thanks
    Michael

  2. #2
    Bob Carnie's Avatar
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    I will ask some of these questions to Dr Mark , he uses very wide angle lenses on his Linhof and I do not think he uses filters.
    If he does not use filters then I would say you are ok not to use them as I have no falloff issues when printing his work at larger magnification.
    I won't be seeing him until the weekend.


    Quote Originally Posted by Michael R 1974 View Post
    I'm in the process of re-outfitting my 4x5 gear for wider angle work. I'm looking at a current 90mm Schneider 5.6 XL, and also a 72mm Schneider 5.6 XL (or possibly a Rodenstock 75mm 4.5 Grandagon N).

    Some questions regarding these ridiculously expensive center filters:

    1) If I'm realistically going to be shooting at f16 or smaller, do I really need these? Even on a 90mm?? Is there that much falloff at working apertures??

    2) In the Rodenstock litterature it says the center filters are optimized for the working aperture (say f16). Ok, what happens if I'm at f22 or smaller? Do you need to remove the filter at smaller apertures than the aperture for which they are "optimized"? Seems to me if falloff decreases as you stop down, at some point falloff is reduced to the point where a center filter would be detrimental, causing the center of the image to be darker than the edges. ?

    3) Are these filters always necessary or only when movements are involved (eg significant front rise typically required in architectural work)?

    Experiences and thoughts welcome.

    Thanks
    Michael

  3. #3
    keithwms's Avatar
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    Haha reminds me of when I thought I needed one for an ultrawide. The darn thing was almost as expensive as the lens! Then I bought it and wound up selling it shortly thereafter. And just for comparison, the lenses you mention aren't nearly as wide as the one I was using at the time (a 55).

    Unless you are shooting colour slide, you can usually get by without a center filter. What you do is expose and develop to make sure that you will have the latitude in your curve, and don't terribly underexpose the edges. And you simply make yourself a circular dodge/burn tool for use at the enlarger. Or if you are working on a screen, there are other methods. With the wide latitude of b&w film and the ease of d&b and contrast control on modern papers, there is seldom a real need for a center filter... though it can be convenient. With slide, you have much less latitude and you have to worry about not being able to d&b as effectively. I mean, some slide films change colour balance as a function of exposure, then it's a mess.
    "Only dead fish follow the stream"

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  4. #4

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    Thanks for the help Bob. Much appreciated. I've also posed the question to John Sexton, who has done work with these lenses that is similar to the projects I'm working on. Falloff might be less of an issue in the house calls pictures since they are more like portraits rather than landscape/architecture. Not sure. Anyhow its a troubling prospect because these things are damn fortune. I can understand the necessity with ultra-wides like 58mm or even shorter, but a 90 is nothing crazy.

  5. #5

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    As has been pointed out, falloff is a worse problem with narrow latitude films, i.e., reversal films. Whether you need a center filter depends on how far you move the lens off center and on how exacting you are.

    Just for curiosity I looked at Schneider's illumination curves for the current 90/6.8 SA. It is down two stops edge of the 216 mm circle covered at f/22. Its down 1 stop at ~ 75mm off-axis, i.e., in the corner of 4x5 when shot straight ahead.

    FWIW, patience in shopping helps. A while back I bought a 35/4.5 Apo Grandagon. With it shooting straight ahead, the corners of a 6x9 tranny are too dark. So I wanted a CF. As you remarked, $$$. So I waited and watched. I eventually lucked into the right CF for that lens for $225 delivered. Used, flawless. And it helps ...

  6. #6
    wildbill's Avatar
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    Pm sent.
    www.vinnywalsh.com

    I know what I want but I just don't know how to go about gettin' it.-Hendrix

  7. #7

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    Thanks for the replies everyone. I'm really struggling with this given how steep the cost is. The problem is - I am VERY exacting. I guess it might come down to good old fasioned testing. It's frustrating though.

  8. #8

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    Just part of the investment in any especially wide angle of view. I can't imagine any high quality color work without one, either chrome or color neg (latitude is only part of the problem). Some black
    and white work might look nice with a degree of symmetrical falloff, or will partially correct itself with
    a matched falloff in the enlarger lens - but you will have potential issues with shift and swing, or with
    pushing the low values onto a different part of the film curve. Experiment awhile to see what can be
    done without one. And if you do buy one, consider the specific quality distinctions between the
    available brands. Anything really good in this category is inherently expensive to make.

  9. #9

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    I guess what I'm most troubled by is the fact I'll pretty much always be working at apertures smaller than f16. So I'm wondering if a center filter is really necessary in that case, particularly with the 90mm.

  10. #10

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    Center filters work poorly at wide apertures. f/16 on down should OK, but I like them better at f/22.
    Make sure you get the proper one for your exact lens. It's important to have the right amount of
    neutral density at the correct distribution. Most of the fast 90's need a stop and a half correction.
    There's an extensive recent thread over on the Large Format Forum about the newest center filter
    designs.

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