Canon Extender 2X II with 300mm 4L IS

Discussion in 'Canon EOS' started by dennis_tam, Oct 31, 2009.

  1. Hi,
    I have a 40D body and want to shoot some birds.
    I purchased canon extender 2X and coupled it with my 135mm 2L and 300mm 4L IS.
    There is good picture quality on extender 2X/135mm 2L.
    However, I can not even get auto focus on extender 2X/300mm 4L IS. Under manual focusing mode of 40D, the picture is quite blurry.
    I checked the compatibilty table offered by Canon and they should be compatible to get AF.
    Does any one have the same combination (extender 2X/300mm 4L IS) that I have? Is there anything I should specifically set on body/lens to get AF?
  2. the combined f stop with the 2x on a f4 lens is f8. this means no auto focus on your 40d.
  3. the combined f stop with the 2x on a f4 lens is f8. this means no auto focus on your 40d.
  4. No AF with your 40D because the effective Aperture is now f/8 and the 40D will only AF up to f/5.6. You could get a non-Canon 2x extender (like the Kenko pro) and tape three pins and have AF in good light (but ONLY in good light) or just buy the 1.4x from Canon instead and your lens will focus just fine on your 40D.
  5. In my tests, the 1.4x with the 300/4 IS and then upsampling via Photoshop produced the same quality as using the 2x. Since the quality was the same and I lost autofocus, I stopped using the 2x with the 300/4.
    For whatever reason, the 2x with the 300/2.8 produces superior results than the 1.4x and upsampling. Not sure why, but that's my personal results. :)
  6. The 1D series will auto focus at f8. Used 1D MkII's have come way down in price.
  7. As Scott says only 1 series bodies have AF at F8 this does include the film bodies and the EOS 3. I do not use the f4 lens but use the F2.8. Even with the 300 F2.8 while you retain Af the 2x TC is not great. I did not buy the Mark I 2xTC but did get the MarkII although I almost never use it as it is very poor compared to the 1.4x TC. The 2X TC is especially bad on zooms like the 70-200 f2.8L
  8. No it will only MF. However it can produce good sharpness with the 2X as long as you focus acuratly. In my tests using
    the 2X tc was always better than using a 1.4X and upscalling.

    however these tests were with a 20D and it is possible that a higher resolution camera may be different, I'll have to check
    with my 7D.

    Of course MF for birds is not too practicle. Surprisingly double stacking the ef 1.4X with a kenko pro 1.4X worked well with
    the 300mm in good light and permits AF. Test for this are findable from the above link.
  9. I bought the 2X II to use with my 300 F4L IS with my EOS 3 which would AF with it.
    I've never had a good result from it. I have had great results with the 1.4X, but never with the 2X. The same is true with the subsequent bodies I've tried it on (20D, 5D). The 2X sits gathering dust.
  10. The 2x on the 300/4L is fine. Focus carefully and stop down a stop and you'll get decent (if not exceptional) results. Technique counts a lot when using the 2x. You may want to use Live View and 5x magnification for focus if your eye's aren't sharp enough.
  11. You could get a non-Canon 2x extender (like the Kenko pro) and tape three pins and have AF in good light (but ONLY in good light)​
    Probably not, Juergen - it's pretty well known that the 40D doesn't play well with taped or non-reporting TCs at f/8: my 40D won't work at all on the centre AF point with a 1.4x and 100-400mm at f/5.6 whereas the same set-up was great on my 30D.
    I know I'm far from alone here (much discussion about it since September 2007 - I think I might have been the first to publicise this fact ) and while odd 40Ds seem to work, more or less, the majority of folk who have contributed to discussions about it report similar lack of success.
    A 300mm f/4 and a 2X will likely be exactly the same.
  12. Just in case you want to consider Canon 1.4x extender - it works well with this lens, but the AF slows down considerably.
  13. Nice moon portrait Bob!
    Well, LV 5X for MF probably will be a bit slow for birding. My old EOS 3 would AF with an F8 lens, but only with the center AF point and in single axis mode. I tried it with my 300 4L and Extender 2x and found it pretty iffy for anything but landscapes. Didn't shoot the moon tho'
  14. Thanks a lot to everybody!
    I can still live with extender 2X/135mm 2L, which gives me 270mm, equivalently. Yes, I can get extender 1.4X later.
  15. I also own the 300mm f4L and the 1.4x. It is a fantastic combination. I don't find that the AF slows down that much, only slightly. I used to own the 2x but I sold it after two weeks. It was not worth using. The 1.4x is far superior.

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