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Thread: Using a Center Filter

  1. #1

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    Question Using a Center Filter

    Is using a center filter any different than using any other filter? I will soon have a Schneider SS-XL 150mm and the center filter for it. I have never used a center filter before.

  2. #2

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    Re: Using a Center Filter

    Yes, a center filter will not work unless the lens is stopped down at least 2 stops.

  3. #3

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    Re: Using a Center Filter

    Bob, I've not heard this. The radial light falloff is a function of aperture at least in the case of the 150 SS-XL and at large apertures? Does this mean these Schneider center filters are designed to function best at certain apertures? Interesting; or are we splitting hairs.

    Nate Potter, Austin TX.

  4. #4

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    Re: Using a Center Filter

    Quote Originally Posted by Nathan Potter View Post
    Bob, I've not heard this. The radial light falloff is a function of aperture at least in the case of the 150 SS-XL and at large apertures? Does this mean these Schneider center filters are designed to function best at certain apertures? Interesting; or are we splitting hairs.

    Nate Potter, Austin TX.
    All center filters need the lens to be stopped down at least 2 stops for the lens to "see" the effect of the filter.

    See third paragraph of the attached Schneider instruction sheet from a new Schneider center filter.

  5. #5

    Re: Using a Center Filter

    Quote Originally Posted by Bob Salomon - HP Marketing View Post
    All center filters need the lens to be stopped down at least 2 stops for the lens to "see" the effect of the filter.

    See third paragraph of the attached Schneider instruction sheet from a new Schneider center filter.
    Bob, that's a really vague description and doesn't really explain the "why" of why you need to stop down other than to have the "full compensation effect". Do you know if there is a white paper or something similar for this? Here is the third paragraph Bob is pointing to:

    When using these Center Filters exposure time should be extended three or resp. four times. Furthermore full compensation effect of the filters is obtained by closing down the lens by two stops at least.

  6. #6

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    Re: Using a Center Filter

    Quote Originally Posted by Jeremy Moore View Post
    Bob, that's a really vague description and doesn't really explain the "why" of why you need to stop down other than to have the "full compensation effect". Do you know if there is a white paper or something similar for this? Here is the third paragraph Bob is pointing to:
    No, Rodenstock states that the center filter works at the recommended aperture of the lens and stopping down further will not improve the fall-off.

  7. #7

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    Re: Using a Center Filter

    What I understand from the above: the center filters are designed for lenses at their optimum aperture.
    That means that using a center filter used at full opening will have a diferent effect, because it is not designed for it.
    Makes sense.

    Peter

  8. #8

    Re: Using a Center Filter

    Quote Originally Posted by Archphoto View Post
    What I understand from the above: the center filters are designed for lenses at their optimum aperture.
    That means that using a center filter used at full opening will have a diferent effect, because it is not designed for it.
    Makes sense.

    Peter
    Yes, the general sense of it makes sense, but I'm just curious if anyone has a pointer to a description of the physics involved. I find the science of optics to be incredibly fascinating. Maybe I'll just dredge out some optics book and see if I can piece a precise explanation myself this weekend.

  9. #9

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    Re: Using a Center Filter

    Quote Originally Posted by Jeremy Moore View Post
    Yes, the general sense of it makes sense, but I'm just curious if anyone has a pointer to a description of the physics involved. I find the science of optics to be incredibly fascinating. Maybe I'll just dredge out some optics book and see if I can piece a precise explanation myself this weekend.
    Jeremy,

    The filters are made for photography so white papers are not part of the support. Photographers want to know how to use them, when to use them and how much light they will lose when they are used. This is the kind of information that is published for users.

  10. #10
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    Re: Using a Center Filter

    I imagine that at large apertures the fall off is greater so the centre filter may not completely compensate.. At some point the decrease in fall off by closing down the aperture stops happending .. this is probably the aperture at which the CF works best..

    Tim
    Still Developing at http://www.timparkin.co.uk and scanning at http://cheapdrumscanning.com

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