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  1. #11
    MattKing's Avatar
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    Quote Originally Posted by Satinsnow
    Matt,

    I would expect a lens designed for 645 to vignette on a 6x9, that seems to reason, All of my Mamiya lenses have square exits at the mount end of the lens, including my 500mm

    Dave
    Dave,

    That is interesting, because none of my other lenses (45mm f/2.8 C - {77mm filter}, 55mm f/2.8 N, 80mm f/2.8 C and 70 mm f/2.8 C {leaf shutter}) have this baffle.

    I too would have guessed that these 645 lenses would have probably vignetted, I just thought that the baffle might make it even more certain.

    By the way, why do you think the baffle is used?

    Thanks,

    Matt

  2. #12
    Dave Parker's Avatar
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    Quote Originally Posted by MattKing
    Dave,

    That is interesting, because none of my other lenses (45mm f/2.8 C - {77mm filter}, 55mm f/2.8 N, 80mm f/2.8 C and 70 mm f/2.8 C {leaf shutter}) have this baffle.

    I too would have guessed that these 645 lenses would have probably vignetted, I just thought that the baffle might make it even more certain.

    By the way, why do you think the baffle is used?

    Thanks,

    Matt
    Matt being honest with you I really don't know, but I have seen all of the lenses you mention, with and without the baffles, It may depend on the the age of the lenses, but I also have many manual focus Minolta lenses that I used on my XD-11 that have the baffles..

    Dave

  3. #13
    MattKing's Avatar
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    Quote Originally Posted by Satinsnow
    The circle of coverage for a 6x9cm would have to be at least 9cm in diameter to give full coverage. It really has nothing to do with the diameter of the lens, but the diameter of the projected image.

    Dave
    Dave,

    Actually, if the circle of coverage is, indeed, a true circle, I think that the circle of coverage would have to be the diagonal of a 6x9cm rectangle, or at least 12.041 cm.

    {its my damned training in physics and math - it goes weeks without being used, and then rears its ugly head at the most surprising moments }

    Matt

  4. #14
    Dave Parker's Avatar
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    Quote Originally Posted by MattKing
    Dave,

    Actually, if the circle of coverage is, indeed, a true circle, I think that the circle of coverage would have to be the diagonal of a 6x9cm rectangle, or at least 12.041 cm.

    {its my damned training in physics and math - it goes weeks without being used, and then rears its ugly head at the most surprising moments }

    Matt
    Matt,

    I already posted a follow-up that I screwed up and engaged keyboard before brain..

    Dave

  5. #15
    MattKing's Avatar
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    Quote Originally Posted by Satinsnow
    Matt,

    I already posted a follow-up that I screwed up and engaged keyboard before brain..

    Dave
    My apologies Dave - of course you did!

    In case you missed it, in all humility I must confess, in pointing out the correction, I screwed up my calculation!

    Matt

    {Note to self - if you are going to respond to a post - first check if poster has already clarified or corrected same, especially when poster is known to be both accurate and careful!}

  6. #16
    Dave Parker's Avatar
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    Quote Originally Posted by MattKing
    My apologies Dave - of course you did!

    In case you missed it, in all humility I must confess, in pointing out the correction, I screwed up my calculation!

    Matt

    {Note to self - if you are going to respond to a post - first check if poster has already clarified or corrected same, especially when poster is known to be both accurate and careful!}
    Don't worry Matt,

    Heck a couple of beers and pizza on Saturday night and I am likly to mess just about anything up.....

    Dave

  7. #17
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    Quote Originally Posted by Satinsnow
    Don't worry Matt,

    Heck a couple of beers and pizza on Saturday night and I am likly to mess just about anything up.....

    Dave
    OK then. New rule. Dave can't grind on Saturday night after Beer and Pizza.

    The lenses for my RB 67 don't seem to have baffles.

    Mike Davis

  8. #18
    Dave Parker's Avatar
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    Quote Originally Posted by jmdavis
    OK then. New rule. Dave can't grind on Saturday night after Beer and Pizza.

    The lenses for my RB 67 don't seem to have baffles.

    Mike Davis
    No problems there Mike, I always try to take Saturday night off to spend with the wife and Puppies, here is a pic of one of the puppies, showing how we all kick back on a Saturday night!

    None of my 67 lenses ever had the baffle either...






    Dave

  9. #19

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    Remember, though, that a standard lens for 6 x 4.5 with be a wide angle on larger formats, so you might want to change lens for that reason.

    David.

  10. #20

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    Quote Originally Posted by Satinsnow
    The circle of coverage for a 6x9cm would have to be at least 9cm in diameter to give full coverage. It really has nothing to do with the diameter of the lens, but the diameter of the projected image.

    Dave
    100 mm, Dave. sqrt(57^2 + 82^2). 90 mm is the diagonal of nominal 6x7.

    Cheers,

    Dan

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