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Double fofal length

  • 12-03-2010 2:50pm
    #1
    dinneenp
    Registered Users, Registered Users 2 Posts: 8,156 ✭✭✭


    Hi,
    can anyone tell me about 'double focal length' (not sure of proper term)?
    In another thread someone said about a 200mm-
    Also on a Olympus the focal lenght is doubled..So it's a 400mm f/3.5

    Obviously it's something that'll double the focal lenght but:

    what is it, how does it work?
    does it compromise quality?
    do you put on an adaptor or something for it to work etc?

    Cheers,
    Pa.


Comments

  • #2
    DaireQuinlan
    Registered Users, Registered Users 2 Posts: 6,703 ✭✭✭DaireQuinlan


    dinneenp wrote: »
    Hi,
    can anyone tell me about 'double focal length' (not sure of proper term)?
    In another thread someone said about a 200mm-
    Also on a Olympus the focal lenght is doubled..So it's a 400mm f/3.5

    Obviously it's something that'll double the focal lenght but:

    what is it, how does it work?
    does it compromise quality?
    do you put on an adaptor or something for it to work etc?

    Cheers,
    Pa.

    The focal length isn't really being doubled. In the DSLR world for some reason the habit has grown of referring to crop factors of the various sensors. These are expressed in terms of a full 35mm film frame (36x24mm). Olympus 4/3rds sensors are roughly half the size of a full frame. As a result a 200mm lens mounted on an Olympus 4/3rds camera will give an equivalent field of view as a 400mm lens mounted on a 35mm camera or full frame DSLR.


  • #3
    duffarama
    Registered Users, Registered Users 2 Posts: 609 ✭✭✭duffarama


    Read this http://www.wrotniak.net/photo/43/sensor-size.html


  • #4
    Morrisseeee
    Registered Users, Registered Users 2 Posts: 5,146 ✭✭✭Morrisseeee


    Yes there are adapters to 'double' or 1.5* your current focal length, of course it all depends on the camera's sensor size, ie. full frame 36*24, or the other variants of 1.5* & 1.6*or Olympus 2*, what that means is the Olympus sensor is half the size of the full frame sensor & hense giving you a half crop of a photo taken with a full frame sensor. This also means their lenses can be small.
    Another take on it is: if you have a full frame camera & you are at a football match, you ideally need a 300mm lens at say f2.8, now thats a big lens, but on an Olympus body camera you would only need a 150mm 2.8 lens to get the same shot, but then the full frame camera can bump up the ISO to 3200 or more to capture the fast action whereas the Olympus will bow out around 400 (or slightly more on an E3).


  • #5
    duffarama
    Registered Users, Registered Users 2 Posts: 609 ✭✭✭duffarama


    Morrisseeee wrote: »
    Another take on it is: if you have a full frame camera & you are at a football match, you ideally need a 300mm lens at say f2.8, now thats a big lens, but on an Olympus body camera you would only need a 150mm 2.8 lens to get the same shot, but then the full frame camera can bump up the ISO to 3200 or more to capture the fast action whereas the Olympus will bow out around 400 (or slightly more on an E3).

    The newer cameras are much better at higher ISO's. Also the 150mm lens available is an F2 so you don't need to bump the ISO as much. Plus you get double the depth of field, which can be a bonus.


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