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Thread: Centre filters

  1. #1

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    Centre filters

    How many of you find you need them for your ULF work? What format and/or lenses?

    I've only shot 4x5, but ULF may be in my future and I'm curious about this. I know there are a lot of process lenses and such with adequate coverage for up to 16x20 and beyond, but in what circumstances do you have to worry about these expensive filters?

    Thanks
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    Quote Originally Posted by walter23 View Post
    ...in what circumstances do you have to worry about these expensive filters?

    Thanks
    With extreme wide-angles, regardless of format.
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    Okay, good to know. That's what I figured. If I understand correctly, off-center light fall-off is simply a consequence of the changing effective shape / size of the diaphragm as you move off center, so with longer lenses (where light is travelling at less extreme angles) you don't have to worry about it so much. Is there another optical reason, beyond just the shape of the diaphragm or lens barrel - kind of like how sunlight is effectively spread out and weakened when it hits the northern hemisphere at an oblique angle in winter?
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    Quote Originally Posted by walter23 View Post
    Okay, good to know. That's what I figured. If I understand correctly, off-center light fall-off is simply a consequence of the changing effective shape / size of the diaphragm as you move off center, so with longer lenses (where light is travelling at less extreme angles) you don't have to worry about it so much.
    Also the fact that the energy transferred by light is proportionate to the fourth power of the cosine of the angle of incidence -- Snell's law, I think -- though most modern lens designs actually do rather better than cos4 might imply. As you say, with longer lenses, the angle of incidence is less extreme so it matters less. A lot less.
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    It depends on what you mean by "ULF." There is one answer for 11x14 / 8x20 and below, and another for 12x20 / 14x17 and above.

    I normally use a center filter with the SS 110mm XL on 8x10 (both B&W and color). I use a center filter when I shoot chromes with the SA 72mm XL and the SS 150mm XL again on 8x10 (warning: the SA 72mm XL does *not* cover completely 8x10!).

    I imagine that the same applies to the SS 210mm XL on 11x14. For the really large formats instead (say 12x20, 14x17 and above) there are no superwide lenses to speak of, let alone center filters that go with them.

    Cheers!

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    Quote Originally Posted by mammolo View Post
    I imagine that the same applies to the SS 210mm XL on 11x14. For the really large formats instead (say 12x20, 14x17 and above) there are no superwide lenses to speak of, let alone center filters that go with them.
    Cheers!
    Okay, so those of you shooting process lenses and stuff with 12x20 aren't suffering from vignette problems? Good.
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    Quote Originally Posted by mammolo View Post
    I imagine that the same applies to the SS 210mm XL on 11x14. For the really large formats instead (say 12x20, 14x17 and above) there are no superwide lenses to speak of, let alone center filters that go with them.

    Cheers!
    The 210mm SSXL covers 8X20, 12X20 and 14X17 with some movement and I certainly consider it to be a superwide for these formats. I would definitely recommend a centerfilter when using this lens with these formats. Even when correction are perfect there is still considerable light falloff because of simple geometric considerations.

    Sandy King

  8. #8
    mammolo's Avatar
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    Sandy,

    wow! I thought the SS 210mm XL could not go up to 12x20 o 14x17. That's great then, a superwide is indeed available for supersize formats.

    Now, speaking of money for the lens and the center filter ... ouch

    One thing that worries me with superwides like the 210mm XL used in ULF is that without really mounting it on the camera it is difficult to make sure the bed does not show up in the frame. Tilting the camera forward may be impractical, it may be impossible to push the rear standard forward as well, some ULF do not have the movements you have in an 8x10 etc etc, and a lens like that can't be returned very easily, at least in Europe (a.k.a. "special order syndrome").

    Any word of wisdom on how to approach the problem?

    Thanks!
    Last edited by mammolo; 09-17-2007 at 09:50 PM. Click to view previous post history.



 

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