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
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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
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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
  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.)

    Alan Browne, Feb 28, 2005
  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).

    Alan Browne, Feb 28, 2005
  6. narke

    narke Guest

    understand. Thank You All
    narke, Mar 1, 2005
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