Help... Can someone educate me on the types of SLR lenses?

Discussion in 'Digital Photography' started by 12991, Jun 18, 2007.

  1. 12991 macrumors member

    Joined:
    Feb 3, 2007
    #1
    Im kind of confused. Wide angle, super wide angle, telephoto, telephoto zoom, zoom?

    Is telephoto just a lens that zooms? Like a 55-200?

    And a wideangle is just like 18-55??

    And a superwide angle would be like 12-24?

    And the only reason why anyone would buy another wide angle assuming theres came with an 18-55mm kit lens is either they want it faster or they want like a 17-70 or something right?

    What are the main categories of the lenses?
    :confused: :confused: :confused: :confused: :confused: :confused: :confused: :confused: :confused: :confused:
     
  2. Lovesong macrumors 65816

    Lovesong

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    Stuck beween a rock and a hard place
  3. epicwelshman macrumors 6502a

    epicwelshman

    Joined:
    Apr 6, 2006
    Location:
    Nassau, Bahamas
    #3
    I'm not sure what you mean by catagories of lenses. You've got it mainly right, a 200mm lens is a telephoto, 18mm is a moderate wide angle, 10mm is an extreme wide angle.

    If I was to replace my 18-55 with, say, the Nikon 17-55 2.8 it wouldn't be for a wider angle; 1mm makes barely any difference. The 17-55 is a constant 2.8 maximum aperture, allowing for better performance at any focal length. It's also a higher quality lens, made of metal instead of plastic and is more durable. It's also about $1000 more than the kit lens, so you definitely pay for it.
     
  4. Grimace macrumors 68040

    Grimace

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    Feb 17, 2003
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    #4
    Canon has a graphically organized way of explaining it on its web site:

    Important terminology: zoom lenses have a variable focal range (ie. 17-55mm) and prime lenses are fixed (ie. 50mm).
     

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  5. ChrisA macrumors G4

    Joined:
    Jan 5, 2006
    Location:
    Redondo Beach, California
    #5
    I think I can make it easy but first look at the camera sensor or film. Draw a line diagonally from corner to corner. If using 35mm film or a so called "full frame" sensor the diagonal line is about 50mm long. The line is shorter on a typical dSLR and longer on a medium format camera. But let's call it "50mm".

    "Telephoto" means a lens longer then the diagonal. An example would be an 85mm lens

    "normal" is the lens that is equal to the diagonal. On a 35mm film camera a "normal" lens is 50mm long

    "Wide" means shorter then the diagonal.

    The terms are many times blurred and people use "round" numbers. So don't take them as exact definitions. Some people are still using the 50mm digonal to define "normal" even if normal on a dSRL is closer to 35mm.

    "Zoom" means a lens that can change it's length.
    Some zooms operate from a wide to telephoto range.
    Others stay in the "wide" range and others are
    "telephoto zooms" because there range is always
    longer thne the diagonal.

    You will also see modifiers used such as "moderate telephoto" or "long telephoto". This just means how much longer the lens is relative to the diagonal of the sensor.

    The above only address the _length_ the other part is the _diameter_ and this is measured with nits called "f-stop". The "stop" is simply the ratio of diameter over lenght. So an f/8 lens has a diameter of length over 8, hence the term "f/8"

    Lenses that are larger diameter let more light through. No maic there, just like a water pipe. Bigger pipe, more water and yes more expensive.

    Today in 2007 technology is such that you can't make a lens without some compromise. A wide to telephoto zoom that opens up to f/2.8 that is small and compact and inexpensive is absolutely not possible. So you have to trade off features and likely buy several lenses. Optical technology is pretty mature so it is not likely to change fast either So don't worry about investing money in optics. Unlike the dSLR body the lenses on the market 20 years from now will likey not be much different then what we have now.
     

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