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  1. #11
    jstraw's Avatar
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    Quote Originally Posted by Solarize View Post
    Thanks for the help all, I think I'm starting to understand this a bit more.

    Just to clarify something... When someone talks about using a wider lens for the speed it offers them, is this only because the lens they are using happens to stop down further than say their standard lens. So a wide angle lens with a minimum aperture of 2.8 is effectively no quicker than a standard lens with 2.8 as the minimum aperture?

    Cheers
    That is correct.

  2. #12
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    Quote Originally Posted by Helen B View Post
    ...f-numbers are used for focus calculations, whether or not T-numbers are used for exposure, because f-numbers are geometrical.
    It's rare that a still photographer needs to worry about T-stops anyway.

    T-stops are most important for movie cameras, because changes in exposure from shot-to-shot break editorial continuity. But still, in general, have no such concept.

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  3. #13
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    Quote Originally Posted by Solarize View Post
    Just to clarify something... When someone talks about using a wider lens for the speed it offers them, is this only because the lens they are using happens to stop down further than say their standard lens. So a wide angle lens with a minimum aperture of 2.8 is effectively no quicker than a standard lens with 2.8 as the minimum aperture?
    I think this idea (of faster speed with a wide lens) is a misconception that results from the fact that short lenses can be handheld for longer exposures. It feels faster, but in reality it's not.
    Paul

  4. #14

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    Regardless of what you want to call it, in terms of a lens w/no front lens cell, you'll caluculate by using the iris diaphragm/aperture, period.
    Jonathan Brewer

    www.imageandartifact.bz

  5. #15
    Christopher Walrath's Avatar
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    God bless. How many times do I need a smack on the back of the head? I knew f-stop numbers were the ratio of focal length to aperture diameter, but I did not figure transmitting the same alues from lens to lens. I am so glad I am here and not at some digital hack group like BP.com.
    Thank you.
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  6. #16

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    I don't know what you mean by 'special', you might call a Kodak portrait lens 'special' in terms of no glass in front the aperture, certainly a convertible lens is more common in LF photography.

    Also, I learned on the way up, and this is probably moreso with a LF lens, the idea of 'slop', that is, I always go wide open and then close down to the taking aperture to eliminate as much as possible any 'slop' in the aperture blades.
    Jonathan Brewer

    www.imageandartifact.bz

  7. #17
    Helen B's Avatar
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    Quote Originally Posted by bjorke View Post
    It's rare that a still photographer needs to worry about T-stops anyway.

    T-stops are most important for movie cameras, because changes in exposure from shot-to-shot break editorial continuity. But still, in general, have no such concept.
    I agree entirely. Thanks for adding the correct perspective.

    Best,
    Helen

  8. #18
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    Quote Originally Posted by Jonathan Brewer View Post
    I don't know what you mean by 'special', you might call a Kodak portrait lens 'special' in terms of no glass in front the aperture, certainly a convertible lens is more common in LF photography.
    By 'special case' I just mean a particular case in which the entrance pupil is the physical iris. I have no idea why you are making such a big thing out of this.

    Also, I learned on the way up, and this is probably moreso with a LF lens, the idea of 'slop', that is, I always go wide open and then close down to the taking aperture to eliminate as much as possible any 'slop' in the aperture blades.
    It's also standard practice in cinematography, which we both work in, I believe.

    Best,
    Helen

  9. #19

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    'I have no idea why you are making such a big thing out of this.'..........

    .............THAT'S RIGHT, you don't have any idea of why I say something, so don't try to guess. I'd appreciate no more off topic comments that get personal. Thanks.
    Jonathan Brewer

    www.imageandartifact.bz

  10. #20

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    Quote Originally Posted by Helen B View Post
    I wonder if it has something to do with usable shutter speed, or the idea that you can use a wide lens at wider apertures for the same depth of field (not entirely true, but it all depends on how you think of depth of field).

    Best,
    Helen
    No need for the reference as this answers my question. I clearly wasn't thinking straight last night.

    Thanks for the clarification on 'stopping down' Helen and thanks to everyone else.

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