Zoom Lens

Discussion in 'Beyond the Basics' started by Harpua, Feb 7, 2006.

  1. Harpua

    Harpua TPF Noob!

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    I will eventually be wanting to buy a zoom lens for my D70S. This is my first SLR so I am very confused on a lot of this stuff. I have been looking at lenses and they are all measured in mm's. Having no experience with this sort of thing though the numbers mean very little to me. I know that a 200mm zoom will not get me as close as a 300mm, but that is about all I know. Is there some way of knowing (other than actually looking through the lens) how much magnification I get from a particular focal length?
     
  2. Big Mike

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

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    You could probably find out the magnification ratio of specific focal lengths on that camera...but that's just a number.

    Try out different lenses in a camera store (if you can). It won't take long to get the feel for how focal length affects field of view.

    One trick is to use an empty slide mount. By holding it in front of you and looking through it, you can simulate the camera's field of view. The closer you hold it, the wider (shorter) the lens would be...the farther you hold the mount...the longer the lens.

    Of course, it would take some experience to know where to hold it, to simulate specific focal lengths.

    Really, all you need to know is that longer lensed have more magnification and therefore a smaller field of view.
     
  3. Rob

    Rob TPF Noob!

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    What I just wrote was complete rubbish, so I've deleted it!

    Rob
     
  4. markc

    markc TPF Noob!

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  5. Harpua

    Harpua TPF Noob!

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    Wow I am learning so much here. I never knew there was a difference between zoom and telephoto. So a telephoto is a prime then?

    Mark thanks for those links. the second one especially was very helpful.

    So basically what I am hearing is that to know how much closer my subject is going to be I am going to have to just play with some lenses to get a feel for them. I was hoping there would be some other way so I could order online without having to go to the store as there are none close enough to me to make that feasible anytime in the near future. Oh well I guess that will just give me more time to save my pennies to get a really great lens.
     
  6. Rob

    Rob TPF Noob!

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    If you want an equivilent which is similar to the say 8x magnification of binoculars, then divide the length in mm by 50. So, a 200mm lens is approximately 4x bigger than what your eye sees. A 50mm lens is approximately what your eye sees.

    Telephoto is a length which on a DSLR is about 85mm ish to about 200mm ish. 200mm+ is super-tele-photo and about 30mm to 50mm is "standard" length. It's just a name to indicate that it magnifies the image, so anything bigger than 50 is really tele. Under 30mm is "wide-angle" and under 20mm is normally into "fish-eye". All numbers are notional and vague!

    Zoom and prime are a completely different thing to think about. Zooms are versatile, primes are sharper and brigher. Generally anyway!

    Rob
     
  7. Harpua

    Harpua TPF Noob!

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    Thanks Rob. That is a tremendous help!
     
  8. kemplefan

    kemplefan TPF Noob!

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    i have a d50 and my zoom is a 70-300 i would highly recomend tthis lense i love it ti is well biult solid and has good quailty, and cost around $150
    it has my vote
     
  9. JOAT

    JOAT TPF Noob!

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    I think you'd find this article interesting explaining zoom and magnification.
    http://www.the-digital-picture.com/Canon-Lenses/Canon-Lens-Magnification-Value.aspx

    So according to this article a 400mm lens would have a 8x magnification.
    My canon 100-400mm would be a 4x zoom.

    simple formula divide max length in mm by 50.


    With that being said a zoom lens with a max of 200mm or 300mm is ideal for most people. For general wildlife you should be looking into a lens at least at 400mm which is the minimum, though at times are too short for small birds.

    Sigma and tamron make some good affordable lenses that go even up to 500mm. I'm not familiar with Nikons lens line up though but i've heard good things about their 80-400mm though it may be too pricey for you.
     
  10. Harpua

    Harpua TPF Noob!

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    Thanks JOAT. I like the formula to divide the focal length by 100 and multiply by 2. That is the type of thing I was looking for. that will help me a lot in eciding what to look at.
     
  11. kemplefan

    kemplefan TPF Noob!

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    this is all great but, realy the best way is to go to a store and look through it
    go to a local stor not a chain if you can
    also most stores have a diagrame that has one picture taken at difernt focal lenghths try looking at that
     
  12. Harpua

    Harpua TPF Noob!

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    Does the distance very from brand to brand and lens to lens? If I were looking at a 300mm Nikkor would that be the same as a 300mm of another brand?
     

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