Is there a formula to convert digital lens focal length to 35mm focal length ?

Discussion in '35mm Cameras' started by narke, Feb 28, 2005.

  1. narke

    narke Guest

    Does it relative to CCD size?
     
    narke, Feb 28, 2005
    #1
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  2. narke

    Justin Thyme Guest

    Yes it is entirely dependent on CCD size. For DSLR's, most are close enough
    to 1.5x. The Olympus E1/E300 are the only lowish-priced SLR's that are
    significantly different, with a 2x equivalence factor.
     
    Justin Thyme, Feb 28, 2005
    #2
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  3. narke

    Chris Brown Guest

    Yes. To a first approximation, divide 43 by the diagonal of the sensor in
    millimetres. This will give you the multiplication factor for field of
    view/focal length (differing aspect rations will make this something of an
    inexact sicence, but it should be close).

    (43mm is the diagonal of a 35mm frame).
     
    Chris Brown, Feb 28, 2005
    #3
  4. narke

    Alan Browne Guest


    The focal length does not change at all.

    The 'cropping' factor gives a final image similar to the effect of using a
    longer lens of FL * cropfactor.

    So, a camera with a 50mm lens and a 1.5 cropped sensor is said to be equivalent
    to a 75mm lens. (But the focal length does not change, the sensor is just smaller.)

    Cheers,
    Alan
     
    Alan Browne, Feb 28, 2005
    #4
  5. narke

    Alan Browne Guest

    Just divide 36 by the width of the sensor. eg: the Canon 20D at 22.5 mm (x):

    36 / 22.5 = 1.6

    (Quicker than (36^2+24^2)^0.5 / (22.5^2+15^2)^0.5 and same result).

    Cheers,
    Alan.
     
    Alan Browne, Feb 28, 2005
    #5
  6. narke

    narke Guest

    understand. Thank You All
     
    narke, Mar 1, 2005
    #6
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