telephoto extender? worth it?

Discussion in 'Digital Photography' started by rweakins, Jul 24, 2008.

  1. rweakins macrumors 6502


    May 3, 2007
    I have been looking at some longer telephoto lenses. I have a canon 70-200 f4L. just curious to see what the reviews on an item like the canon telephoto 2x extender i could get and make sure it's compatible with a rebel xt as well as a 40D
  2. rweakins thread starter macrumors 6502


    May 3, 2007
    meaning is the extender a good enough product to "substitute" for a longer telephoto lens
  3. R.Youden macrumors 68020


    Apr 1, 2005
    I am in a similar situation.

    I have the 40D with the 70-200mm f4

    From what I can understand the 1.4x and 2x are good devices. The downside with the 2x is you loose a bit of picture quality and you get no autofocus which is a shame. But it is a damn sight cheap than buying a new 400mm lens. There is a very good review here:

    Digital Picture Review

    Let me know how you get on, I am very interested in the extender too.
  4. Kebabselector macrumors 68030


    May 25, 2007
    Birmingham, UK
    I have the 1.4ex for use with my 70-200 f/4 and my 300mm f/4. It's nice to be able to have slightly longer lenses but I personally don't think it's a substitute for a the real thing (though, the reality is money. The £200 I spent on the 1.4ex got me a 420mm f/5.6 IS lens - which I guess isn't too bad).

    I found performance not too bad, but the images are a little softer with the 1.4x (and apparantly worse with the 2x).
  5. rweakins thread starter macrumors 6502


    May 3, 2007
    darn being a broke college student who can't afford, or even come close to affording, the glass he wants
  6. compuwar macrumors 601


    Oct 5, 2006
    Northern/Central VA
    In general, I find 2x teleconverters to be not able to produce images up to my standards when mated with a prime lens designed to go with the converter. However, you may have different standards of acceptable for your images- so if you have a place where you can try one out, you may find you can accept the trade-off.

    I'm generally ok with 1.4x TCs, though on some zooms they just don't seem to work well at all. Nikon offers a 1.7x that matches the long superteles well enough to be just inside acceptable for me, but that's with a very stable shooting platform and reasonable shutter speeds- but a 2x TC is just too much of an image quality trade off for me. Others seem to get good images with them, but I'm very picky and haven't been able to reproduce their results despiite a lot of experience with long lenses.
  7. ChrisA macrumors G4

    Jan 5, 2006
    Redondo Beach, California
    Most people find that the 1.4X extender is the best one to get.

    The 2X extender causes your lens to loose two stops. Making an f/4 lens and f/8 lens. But read the specs on your camera body. I think you need at least f/5.6 to make the auto focus work. If you use a 1.4X extender then you loose only one stop so your f/4 lens becomes an f/5.6 lens and will still auto focus

    The math is not complex. f-number is simply the focal length over the lens diameter. A 2X extender makes the lens twice as long but the diameter remains the same, so the f-number doubles which means two stops. ("stops" are set up so that each doubles the effective square area of the lens' front element, hence the progression 2, 2.8, 4, 5.6, 8,...)

    The 2X extender is only really usable on a fast f/2.8 lens. It will turn one of those nice fast lenses into an f/5.6 lens which is still usable.
  8. pinktank macrumors 6502

    Apr 5, 2005
    1.4 one is very useful for bird photographers and the like

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