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Thread: Lens question

  1. #1

    Default Lens question

    Hi all,

    Newbie here in terms of lenses, just have a few questions in mind.

    I saw lens like
    28-135mm
    70-300mm

    If let's say I divide 135/28 = 4.8
    300/70 =4.2

    Does it means that they can zoom at the same range? or the bigger the mm means it can zoom more? still a little bit confuse.

    Thanks

  2. #2

    Default

    What zoom really means is how much difference there is between the tele and wide setting.

    The actual angle of coverage/view of the lens depends on its focal length(mm).

  3. #3
    vince123123
    Guests

    Default Re: Lens question

    What you have done is to simply calculate teh zoom ratio, so a 28-135 lens has a ration of 4.8x, and your 70-300 has a ratio of 4.2x, not unlike those you see in videocams or digital cams which advertise a zoom ratio of 3.0x or 5.0x

    to answer your question, the mm means the focal length of the lens. at the risk of simplifying, the lower the mm number, the wider the lens, ie at 28mm is a wide angle, 300 is a telephoto.

    zooming more or less is an ambigious term. for a 28-135 lens, it means that it can zoom from 28mm (wide angle) to 135mm (short-mid telephoto)

    likewise the 70-300 can zoom from a focal length of 70mm (short telephoto) to 300mm (telephoto).

    hope that helps

    Cheers


    Originally posted by sonix
    Hi all,

    Newbie here in terms of lenses, just have a few questions in mind.

    I saw lens like
    28-135mm
    70-300mm

    If let's say I divide 135/28 = 4.8
    300/70 =4.2

    Does it means that they can zoom at the same range? or the bigger the mm means it can zoom more? still a little bit confuse.

    Thanks

  4. #4

    Default

    the longer the focal length, the higher the magnification of the image. that's optical physics.

    zoom ratio is also the magnification ratio.

  5. #5

    Default

    Great thanks for the explanation, I understand now

    now I'm still wondering to get 24-85mm or 28-135mm for my new 10D.

    I tried 24 - 85mm but not 28-135 yet... 24 mm * 1.6 is around 38.4mm which is just nice, close to 35 mm.


    Any suggestion which one to get, price difference is quite high tho but at the same time i love the 24mm too.

    Regards,
    Sonix

  6. #6
    Member
    Join Date
    Feb 2003
    Location
    In the void.
    Posts
    1,323

    Default

    IMO, the 24-85mm isn't such a good lens; the edge definition isn't good and there's quite a fair amount of distortion at the 24mm end. Think you will be better off with the 28-135mm.

    Also, you might also want to wait for the new 17-40mm lens if you are into wide angles.

  7. #7

    Default

    Ok thanks a lot, I think I will go for the 28-135mm, eventhough it's quite pricey.. it think around $900+...

    Thanks for the reply

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