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  1. #11

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    Quote Originally Posted by Ian C View Post
    There's a simple calculation that lets you do this fairly easily based on the lensmaker’s equation

    1/f = 1/i + 1/p

    where f = focal length of the lens, i = image-to-diaphragm distance, and p = subject-to-diaphragm distance.

    Knowing any two of these three variables allows calculating the third. f is known and we choose p, so all we need is
    [...]
    What you do not know is where the principal planes are, relative to the film, to the subject and to the diaphragm.
    So don't use the simple infinitely thin lens formula for anything but an approximation. Results including fractional millimeters will be off the mark by a factor at least ten times the precision suggested by the fractional part.

  2. #12

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    The Helios 44-M is made for M42 cameras, flange-to-film distance 45.5 mm. The OP's link says "Working statement, mm: 45,5 "; a poor translation ...

    I don't know what the OP means by "if that distance was set for 35mm." If he means setting the lens 35 mm from the film, whatever that means, he'll get no usable image.

    The lens is made to cover 24x36, i.e., a 43 mm circle. Until proven otherwise, that's all it will cover. So it will be useless on a larger format.

    OP, its time to acquire the concept "coverage."

    QG, you should be ashamed of yourself.

  3. #13

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    Quote Originally Posted by Dan Fromm View Post
    QG, you should be ashamed of yourself.
    I should?

  4. #14
    Ian Grant's Avatar
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    Quote Originally Posted by Dan Fromm View Post

    OP, its time to acquire the concept "coverage."

    .

    Isn't that the size of the girls swimming costumes on the beach at this time of year

    Ian

  5. #15

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    I thought it was the number of pages available for an assignment for, say, the Swim Suit Special.

  6. #16

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    Here's a helpful chart for flange to film plane distances. I originally thought this was going to be a thread about LF, else I would have posted this earlier. Who would have thought?

    http://www.graphics.cornell.edu/~wes...-register.html


    .

  7. #17
    Ian Grant's Avatar
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    That's a useful page, thanks.

    Ian

  8. #18

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    Quote Originally Posted by Q.G. View Post
    I should?
    Absolutely.

    The OP's question was fairly specific. You replied with vague generalities. I'm sure that if you'd have stopped to think for a moment, as you usually do, you'd have posted an appropriately specific response.

    Cheers,

    Dan

  9. #19

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    Quote Originally Posted by Dan Fromm View Post
    Absolutely.

    The OP's question was fairly specific. You replied with vague generalities. I'm sure that if you'd have stopped to think for a moment, as you usually do, you'd have posted an appropriately specific response.

    Cheers,

    Dan
    ???

    "Vague generalities"???

    What i posted was a warning, that using the formulae suggested by someone else could not lead to the desired result.
    That was very specific.

    So what was really bothering you, Dad, uhmm... Dan?
    Last edited by Q.G.; 07-03-2010 at 07:08 AM. Click to view previous post history. Reason: Used an expression only i knew existed. Colloquial english wants to be mastered. ;)

  10. #20

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    QG, I gave the relevant answer, viz., the lens in question's flange-to-film distance. Your post was correct, as nearly all of your posts are, but irrelevant.

    Is that clearer, son?

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