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Thread: Canon ef20-35 f3.5-5 mount on 500D

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    Default Canon ef20-35 f3.5-5 mount on 500D

    Anybody can share with me regarding above lens as I knew is 94 degree, how come picture that I take not so wide? Even smaller than lens 18-200-60++ degree, any difference within EF lens and EF-S lens?

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    Default Re: Canon ef20-35 f3.5-5 mount on 500D

    Quote Originally Posted by alexloh View Post
    Anybody can share with me regarding above lens as I knew is 94 degree, how come picture that I take not so wide? Even smaller than lens 18-200-60++ degree, any difference within EF lens and EF-S lens?
    on 500D, it is an APS-C camera, with 1.6X crop factor.
    Thus, 18 -200 = 28.8- 320 equivalent (on 35 mm)

    So, 20-35 is only 36 - 56.

    EF can be use on any canon camera, be it crop or Full frame
    EFS can only be use on crop

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    Default Re: Canon ef20-35 f3.5-5 mount on 500D

    Mhy the diagonal angle of view become smaller? because of 1.6x crop so will reduce the diagonal angle? only use ef-s lens will be 1:1 ?

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    Default Re: Canon ef20-35 f3.5-5 mount on 500D

    Mhy the diagonal angle of view become smaller? because of 1.6x crop so will reduce the diagonal angle? only use ef-s lens will be 1:1 ?
    Even on an ef-s lens, you'll still experience the 1.6x perspective.

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    Default Re: Canon ef20-35 f3.5-5 mount on 500D

    Quote Originally Posted by alexloh View Post
    Mhy the diagonal angle of view become smaller? because of 1.6x crop so will reduce the diagonal angle? only use ef-s lens will be 1:1 ?
    The crop factor is a size ratio between sensor / media size and the focal length of the lens. Since the focal length remains unchanged (cause it's depending on the glass elements) using a smaller sensor (APS-C) will result in the crop effect / crop factor.
    EF-S lenses have the focal length as stated on the lens but have the "short back build" - putting the back element closer to the sensor. More here: http://en.wikipedia.org/wiki/Canon_EF-S_lens_mount

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    Default Re: Canon ef20-35 f3.5-5 mount on 500D

    So that if I mount a uwa EF lens on my 500D sure cannot get the ultra wide diagonal angle only can get ratio 3:2 of the specification of the lens rite? Only mount on ff body just can get the exactly diagonal angle as show on lens's spec?

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    Default Re: Canon ef20-35 f3.5-5 mount on 500D

    it's more exactly 1.6 x the focal length to get the "mm equivalent" on a full frame that most people are familiar with.

    it's definitely confusing unlike the small digicams that mainly advertised the full frame equivalent focal length. but even so, if u look at the lens, they usually still state the exact specs. for e.g. my fujfilm f100d is 28-140mm equivalent for its 6.4 to 32mm lens.
    Last edited by mpenza; 5th August 2009 at 02:20 PM.

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    Default Re: Canon ef20-35 f3.5-5 mount on 500D

    So I better use the ef-s lenscheaper and get the exact diagonal angle as show on spec, tks for sharing.

  10. #10

    Default Re: Canon ef20-35 f3.5-5 mount on 500D

    Quote Originally Posted by alexloh View Post
    So I better use the ef-s lenscheaper and get the exact diagonal angle as show on spec, tks for sharing.
    it's not that specs are wrong, it's just that full frame (EF) lenses are shown with 1x crop factor results, ef-s (or crop frame) lenses are shown with different crop factor (1.6x) results.

    as a rule of thumb, if you are using 8000 different lenses on one camera, the shorter focal length will always have a bigger diagonal angle.

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    Moderator Octarine's Avatar
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    Default Re: Canon ef20-35 f3.5-5 mount on 500D

    Quote Originally Posted by alexloh View Post
    So I better use the ef-s lenscheaper and get the exact diagonal angle as show on spec, tks for sharing.
    Do note that there aren't that many EF-S lenses than EF lenses. Ok, 3rd party vendors add a few but still EF lenses make the majority in the line-up. Also do note that many EF lenses perform a bit better on crop sensor body because of the smaller image circle. Soft corners and vignetting are less pronounced (or don't exist) on smaller sensors. So it makes a lot of sense to look for EF lenses.
    What exactly is your point? If unsure whether a lens is wide enough go and rent / borrow the lens and try instead of pondering over diagrams and numbers. If you don't have any FF or film camera there's no point drooling over supposedly wider field of view.

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