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Thread: Should I get a center filter for my 65mm Nikon-SW f/4 & 90mm Sinaron-W f/6.8?

  1. #21

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    Re: Should I get a center filter for my 65mm Nikon-SW f/4 & 90mm Sinaron-W f/6.8?

    Quote Originally Posted by Alan Klein View Post
    Greg: If lens movements change falloffs with center filter masks, are there falloffs with regular lenses, let's say 150mm, if you use movements or for that matter when you use center filters on 75mm lenses?
    PMFJI. Alan, movements increase the angle between the lens' axis and the edges and corners of the gate. The larger the angle, the worse the falloff. This is true for all lenses.

    Center filters don't cause falloff, they approximately correct it by being denser at the center than at the edge.

  2. #22

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    Re: Should I get a center filter for my 65mm Nikon-SW f/4 & 90mm Sinaron-W f/6.8?

    The amount of light fall-off at the edges decreases with reduction in size of aperture. At F22-F32 it becomes almost non-existent or very easily correctable in PS by applying Curves masked with radial gradient. In any cases a slight light fall-off "helps" to the image. I have a center filter but almost never use it as in most cases my A is at F22-F32 and +2 stops filter factor is too high of a price for what it does.

  3. #23

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    Re: Should I get a center filter for my 65mm Nikon-SW f/4 & 90mm Sinaron-W f/6.8?

    Hi all,

    So I contacted Igor Camera regarding their Heliopan 67mm center filters. They have two in stock, but according to the person who I spoke with over the phone, the barrel on both copies is engraved as they are/were rental filters. I naturally asked if there were any scratches on the filters and was told that while there weren’t any major scratches, there may be some light scratches, which didn’t exactly reassure me.

    So I’m back to my hunt for a 67mm Schneider III, Rodenstock E67/86, or Heliopan 67mm ND 3x center filter.

    Can you guys point me to any other resources of where I might be able to find these LF unicorns (besides Craigslist and eBay)?

  4. #24

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    Re: Should I get a center filter for my 65mm Nikon-SW f/4 & 90mm Sinaron-W f/6.8?

    Quote Originally Posted by manfrominternet View Post
    Hi all,

    So I contacted Igor Camera regarding their Heliopan 67mm center filters. They have two in stock, but according to the person who I spoke with over the phone, the barrel on both copies is engraved as they are/were rental filters. I naturally asked if there were any scratches on the filters and was told that while there werenít any major scratches, there may be some light scratches, which didnít exactly reassure me.

    So Iím back to my hunt for a 67mm Schneider III, Rodenstock E67/86, or Heliopan 67mm ND 3x center filter.

    Can you guys point me to any other resources of where I might be able to find these LF unicorns (besides Craigslist and eBay)?
    Did you ask Samyís?

  5. #25

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    Re: Should I get a center filter for my 65mm Nikon-SW f/4 & 90mm Sinaron-W f/6.8?

    Quote Originally Posted by SergeyT View Post
    The amount of light fall-off at the edges decreases with reduction in size of aperture. At F22-F32 it becomes almost non-existent or very easily correctable in PS by applying Curves masked with radial gradient. In any cases a slight light fall-off "helps" to the image. I have a center filter but almost never use it as in most cases my A is at F22-F32 and +2 stops filter factor is too high of a price for what it does.
    Which lens do you use it on?

    Stopping down has no effect on cos^4. It does reduce mechanical vignetting, which is why Rodenstock and Schneider recommend that w/a lenses be stopped down at least two stops from wide open when a CF is attached. The CF can't offset the effects of mechanical vignetting.

  6. #26
    Alan Klein's Avatar
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    Re: Should I get a center filter for my 65mm Nikon-SW f/4 & 90mm Sinaron-W f/6.8?

    Quote Originally Posted by Dan Fromm View Post
    Which lens do you use it on?

    Stopping down has no effect on cos^4. It does reduce mechanical vignetting, which is why Rodenstock and Schneider recommend that w/a lenses be stopped down at least two stops from wide open when a CF is attached. The CF can't offset the effects of mechanical vignetting.
    What is mechanical vignetting as opposed to cos^4 vignetting? Why do Rodenstock and Schneider recommend that wide angle lenses be stopped down two stops when a CF is attached but not when it isn't attached? Wouldn't mechanical vignetting occur in both situations?

  7. #27

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    Re: Should I get a center filter for my 65mm Nikon-SW f/4 & 90mm Sinaron-W f/6.8?

    Alan, take out a lens. Any lens. Open its diaphragm completely. Hold the lens at arms length. Look through it. Straight through is. Rotate it slowly and watch what happens to the exit pupil. As you rotate it, the end of the barrel will begin to occlude it. The more you rotate it, the less of the exit pupil will be visible. That's mechanical vignetting.

    Now stop the lens down at least two stops and repeat the exercise. You'll find that the lens can be rotated through a larger angle before the end of the barrel begins to occlude the exit pupil.

    Now do you have the idea?

    I can't read minds, have no idea why Rodenstock and Schneider don't recommend stopping down when not using a CF. They might have believed that thoughtful well-informed photographers would know what to do. But and however, there's not much benefit from shooting a w/a lens wide open with a CF attached since the CF can't put back what the end of the barrel took away.

    Cos^4 is purely optical.

    The only way to reduce mechanical vignetting is to stop down. If, that is, you have a lens that's been designed and built. Ross made some lenses engraved E.M.I. for Extra Marginal Illumination with oversize front and rear elements to reduce mechanical vignetting.

  8. #28

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    Re: Should I get a center filter for my 65mm Nikon-SW f/4 & 90mm Sinaron-W f/6.8?

    Quote Originally Posted by Alan Klein View Post
    What is mechanical vignetting as opposed to cos^4 vignetting? Why do Rodenstock and Schneider recommend that wide angle lenses be stopped down two stops when a CF is attached but not when it isn't attached? Wouldn't mechanical vignetting occur in both situations?
    The reason is that the center filter will not have any effect until you stop down at least two stops.

  9. #29

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    Re: Should I get a center filter for my 65mm Nikon-SW f/4 & 90mm Sinaron-W f/6.8?

    Quote Originally Posted by Bob Salomon View Post
    Did you ask Samy’s?
    Believe it or not, I was at the main Samy’s branch (on Fairfax Ave.) and asked them about it two weeks ago. I was asked to leave my contact number and that someone should contact me shortly, either if they have one in their used department or if they can order one.

    As they haven’t yet called, I just called them now to get a status update and was told that these center filters come around once in a blue moon. The person I was speaking with said that she doesn’t even remember the last time she saw a stand-alone center filter.

    Guess these things really are LF unicorns...

  10. #30

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    Re: Should I get a center filter for my 65mm Nikon-SW f/4 & 90mm Sinaron-W f/6.8?

    Quote Originally Posted by manfrominternet View Post
    ... these center filters come around once in a blue moon. The person I was speaking with said that she doesn’t even remember the last time she saw a stand-alone center filter.

    Guess these things really are LF unicorns...
    Hmm. I have a Schneider CF III, paid <$200 for it delivered. No scratches. Finding it took a while. You have to be patient.

    If I were you, I'd buy one of Igor's filters with the right of return. Ask him if he'll do that.

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