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Dumb question about "crop factor"

Discussion in 'Photography Forums' started by Oddbodd, Aug 22, 2005.

  1. Oddbodd

    Oddbodd
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    Have I got this crop factor thing right here guys.....If I had a 20D with a 100-400L lens fitted, would that equate to a 160-640 using the 20D's (1.6) crop factor?
    Then I fit a 1.4x converter does that then equate to a 224-896? :eek:
    or am I just being dumb, please explain.
    Cheers,
    Oddbodd.
     
  2. mr jones

    mr jones
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    yup

    just multiply the lens length by the cop factor

    so 100mm becomes 160mm and so on

    add a multiplier and yes i guess you multiply the lens by 1.4 and then multiply that by 1.6 so 224mm yeh

    unless im wrong!
     
  3. sorbiegunner

    sorbiegunner
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    The down side of this, of course, is that wide angle lenses are also affected by the 1.6 factor, so your really expensive 28mm wide angle lens delivers approx the same angle of view as a standard 50mm lens (45mm actually). This means that wide angle photography on canon/nike systems becomes really expensive and actually impossible at the extreme end.
    Although the new D5 will address this problem with a full 35mm frame sensor.
     
  4. Peakoverload

    Peakoverload
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    Yep you got it right Oddbod although dont forget, as you mention, it is a crop factor and not a multiplication factor. Therefore any lens attached to a non full frame DSLR will give a different angle of view compared to a lens of equivalent focal length on a 35mm SLR or full frame DSLR.

    In other words lets say you have a 100mm lens on your 20D which then gives an effective focal length of 160mm.

    You then take a 35mm camera (or full frame DSLR) and put a 160mm lens on it.

    The angle of view between the two cameras and two lenses, even though they are effectively at the same focal length, will be different with the 35mm camera giving a slightly wider angle of view.
     

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