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Thread: extenders?

  1. #1

    Default extenders?

    Hi all,

    wanna check with you all about extenders?

    i was looking at the canon 1.4x II extender, and i was thinking how does it work?

    do i just attach it to the front of the lens and have my focal length extended by 1.4 times?

    and if i'm using a dslr of 1.6 crop, does it mean that i will double my focal length???

    and will using a extender decrease the lens IQ? or increase vigineting?

    thanks alot guys!
    "For God loved the world so much that He gave His one and only Son" He Love all of us...

  2. #2
    Member lennyl's Avatar
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    Default Re: extenders?

    Quote Originally Posted by evoben View Post
    do i just attach it to the front of the lens and have my focal length extended by 1.4 times?

    and if i'm using a dslr of 1.6 crop, does it mean that i will double my focal length???

    and will using a extender decrease the lens IQ? or increase vigineting?
    It goes between your lens and camera body. It multiplies your focal length by 1.4x (or 2x for the 2x extender, obviously).

    The 1.4x also reduces your light by 1 stop. If you have a f/5.6 aperture lens, that now becomes a f/8 lens, and you will not be able to auto-focus except with 1 series body. The 2x reduces light by 2 stops.

    The extender is not compatible with all lenses. Check compatibility first. Kenko is supposed to have extenders that work with EF-S lenses.

    You multiply the crop factor with the extender's multipler to give equivalent FOV, not add. So it's 2.24x.

    Somewhat off topic :

    1.6 crop cameras do not increase your focal length, the focal length remains unchanged - it gives you a FOV that appears to be equivalent from a lens with 1.6 times the focal length, but your DOF remains unchanged. But if you really want to think of it that way, with a 1.4x extender on a 1.6x crop body, your FOV will be similar to a lens 1.6 * 1.4 = 2.24x the focal length of same lens on a full frame camera.
    Last edited by lennyl; 20th June 2008 at 03:32 PM.

  3. #3

    Default Re: extenders?

    Quote Originally Posted by lennyl View Post
    You multiply the crop factor with the extender's multipler to give equivalent FOV, not add. So it's 2.24x.

    Somewhat off topic :

    1.6 crop cameras do not increase your focal length, the focal length remains unchanged - it gives you a FOV that appears to be equivalent from a lens with 1.6 times the focal length, but your DOF remains unchanged. But if you really want to think of it that way, with a 1.4x extender on a 1.6x crop body, your FOV will be similar to a lens 1.6 * 1.4 = 2.24x the focal length of same lens on a full frame camera.
    An easier way to see is for example, 50mm lens,

    You will get 50 X 1.6 X 1.4 = 112mm
    Meow!

  4. #4

    Default Re: extenders?

    ok...

    so using a extender actually would give me 1 stop lesser huh?

    so if i'm using a F4 constant?

    what would happen?
    "For God loved the world so much that He gave His one and only Son" He Love all of us...

  5. #5
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    Default Re: extenders?

    F5.6 if im nt wrong?
    Pentax K100D Super

  6. #6

    Default Re: extenders?

    Quote Originally Posted by evoben View Post
    ok...

    so using a extender actually would give me 1 stop lesser huh?

    so if i'm using a F4 constant?

    what would happen?
    1.4x = about 1.5 f-stops less.
    2x = 2 f-stops less.

    You do the calculations yourself.

  7. #7

    Default Re: extenders?

    ahh ok... thanks alot guys!!
    "For God loved the world so much that He gave His one and only Son" He Love all of us...

  8. #8
    Member lennyl's Avatar
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    Default Re: extenders?

    If you're interested, read the very brief review here.

    http://www.the-digital-picture.com/r...er-Review.aspx

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