Focal length, format size, and hand holding?

Discussion in 'Beyond the Basics' started by ksmattfish, May 23, 2005.

  1. ksmattfish

    ksmattfish Now 100% DC - not as cool as I once was, but still

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    Something that I've never been able to figure out clearly...

    If the general statement for hand holding (and I know it's very general, and doesn't take into acount other important aspects) is "safe shutter speed equals the reciprocal of the focal length", does this change with format size? Is this idea based on 35mm format, or all formats?

    For instance, I have a DSLR (with the x1.6 size sensor), a 35mm SLR, and a 6x7 SLR, and I put a 50mm lens on each of them, is the general safe hand held speed 1/50th (or round up to 1/60th) for all of them? Or is it more like 1/30th for the 6x7, 1/50th for the 35mm, and 1/80th for the DSLR?
     
  2. hobbes28

    hobbes28 Incredible Supporting Member

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    I think it mostly depends on how steady of a hand you have. I can hand hold a 50mm at as slow as 1/2 second sometimes but on other days I shake at 1/125.

    As for the "safe" rule, I think it applies the same for all formats. I also think you should take into account the crop ratio for the DSLRs because it is a smaller sensor so it changes your focal length in theory. Now don't take that information to the bank but I have been just recently figuring out all the parts of the crop ratio and how that all works so I think we're on the same page at this point. :D
     
  3. ksmattfish

    ksmattfish Now 100% DC - not as cool as I once was, but still

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    I guess what I am asking is does it really have to do with focal length, or is it the magnification/angle of view?
     
  4. hobbes28

    hobbes28 Incredible Supporting Member

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    I would think it was all about the focal length because it's like aiming a gun..the farther you are away from the target, the more of a difference little moves make.
     
  5. Daniel

    Daniel TPF Noob!

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    I think the angle or field of view is important, but I'm not that technical, so I can't explain it.

    I found this discussion on the net, which has some technical detail:
    http://photography-on-the.net/forum/showthread.php?t=56534

    What do you think? Does that make sense what he is saying?

    Edit:

    I was thinking, since you are practicly enlarging (a part of) the image compared to 35mm (or larger), you are also enlarging the camera shake that has been captured. To compensate for it, you need faster shutter speed to reduce the amount of visible shake, don't you?
     
  6. ksmattfish

    ksmattfish Now 100% DC - not as cool as I once was, but still

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    That is how it makes sense to me; magnification is the key rather than focal length. But I've never been able to get a definative answer.
     
  7. tr0gd0o0r

    tr0gd0o0r TPF Noob!

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    Just stick to shooting high aperture, low iso shots with the medium format and keep the tripod handy so you don't have to worry about it

    In all seriousness though, i'd have to agree that it would change.
     
  8. Christie Photo

    Christie Photo No longer a newbie, moving up!

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    ^^^This sounds right to me.^^^

    So, with the larger formats, shorter shutter speeds would be necessary. Combine this with the larger physical size of the camera and I think it's even more clear, making it the other way around... the smaller the format and the shorter the focal legnth, the longer you can make hand-held exposures with acceptable sharpness.
     
  9. pursuer

    pursuer TPF Noob!

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    Wouldn't it be the opposite? When comparing different formats it's not the focal length that is important but the magnification achieved.

    Magnification = focal length / sensor or film size

    So the larger the format the less magnification there is at a particular focal length. That is why the smaller sensors on some DSLRs effectivly increase focal length or more precisly magnification.
     

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