Zoom Question

Discussion in 'Digital Discussion & Q&A' started by Miaow, Feb 10, 2008.

  1. Miaow

    Miaow TPF Noob!

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    This may be a really stupid question lol

    But a couple of days ago got (well my boyfriend did and is mine to use also) a Cannon EOS 400d which has a 75-300mm zoom.

    Anyway i took a pic of something using the 300mm setting which i was showing to someone who has a P&S - Being mainly used to P&S in the past with optical zoom - I was wondering how you would equate a pic taken on 300mm with an optical zoom amount on a P&S to compare it - ie X???

    Thanks
     
  2. Big Mike

    Big Mike I am Big, I am Mike Staff Member Supporting Member

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    The standard for comparison is 35mm film. Your camera has a 'crop factor of 1.6, so at 300mm you compare to the filed of view on 35mm of a 480mm lens.

    P&S cameras also use this same comparison...you can look up the specs of most digital cameras on www.dpreview.com
     
  3. Miaow

    Miaow TPF Noob!

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    Hmm i should add I'm blonde - thats gone over my head a little lol
    Ok so to covert that to a optical zoom rating would it be something like 480/35? So about x13.7?
     
  4. Helen B

    Helen B TPF Noob!

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    The zoom ratio is simply the ratio of the longest focal length to the shortest, so a 75-300 is a 4x zoom. (300/75)

    However, as a P&S usually starts out with something like a 35 mm equivalent, and you end up with a 480 mm equivalent, your calculation is about right: a P&S would have to have about a 13x zoom to have the same 'reach' as your lens at 300 mm.

    Don't expect the same zoom ratios on a camera with the size of sensor that your 400D has as on a P&S with a much smaller sensor. It is much easier to make zooms with a high zoom ratio for cameras with small sensors.

    Best,
    Helen
     
  5. Miaow

    Miaow TPF Noob!

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    Thanks for the Help Helen B & Big Mike:)

    Most people I know (including myself till now really) are more used to hearing a zoom amount in X... rather than mm i so its good to be able to compare the 2 in a value people will understand more lol
     
  6. Garbz

    Garbz No longer a newbie, moving up!

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    yes unfortunately this doesn't tell you much about the lens other than the higher the zoom factor the less likely it is to be a quality lens.

    Afterall Nikon make a 200-400mm and 28-50mm, both have a 2x zoom range but both are very different lenses.

    Many P&S cameras have the mm range written on the front too. The numbers will be ludicrously small like 3-12mm or something. Multiply this by the extremely high crop factor on most P&S cameras (anything from 2-8 i've seen) and you have a basis for comparison again.
     

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