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Roland W
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Re: long lenses - selecting and buying


I am a long time user of the Canon 300 f2.8 L IS lens, and highly recomend it if you want the large aperture at this focal length. I owned the Canon 2X II extender, but did not use it that much, mostly because of not liking the image quality I got, especially near wide open on the 300. I now have the 2X III extender, and have used it a fair amount. I am liking the image quality, and am satisified with the autofocus speed when used on my 1DX, but have not tried the combination on a 7D. But I have not shot high speed birds in flight with the combination, only the kind of big birds you find at air shows, which can be chalenging, but only rarely require very high rate tracking while shooting. So the potential use of the combination will depend on how fast the birds or wildlife are.

The way I remembered it, the information about the Canon series III extenders when they were released stated that the autofocus speed improvement was tied to using the extender with one of the new Canon series II super telephoto lenses, and required special communication between the extender and the lens. But this thread got me looking back at what was actually published, and I found the following article by Canon\'s Chuck Westfall:

http://www.learn.usa.canon.com/resources/articles/2011/updates_supertelephoto_article.shtml

Near the very end of his article, there is a paragraph that includes the following:

\"As with previous EF Extenders, usage of Series III EF Extenders lowers AF drive speed to improve AF performance. When Extender EF 1.4X III is used, AF drive speed is reduced by 50%. When Extender EF 2X III is used, AF drive speed is reduced by 75%. This may seem like a drawback, but in reality subject tracking performance remains quite high when Series III Extenders are used with IS II lenses. This is due to improvements in AF precision made possible by the new microcomputer in the extenders.\"

That statement is not totally clear about how much better the series III extenders are compared to the series II, but does kind of imply that the best improvement is with series II lenses. This paragraph is also likely the source of the \"75%\" number that was mentiond eariler in this thread, but the number was not an improvement value, but rather how much the autofocus speed is REDUCED from normal when you put a 2X series III extender on compared to no extender. It make no sense to me at all that the previous statement about 75% was an improvement value, and this quote I think clears that up. But this quote does not say exactly how much improvement the III gives over a II extender.

I think that the 300 f 2.8 L IS with extenders would be a big step up compared to the 100-400, but the 300 is not a zoom, and is is clearly a lot more to handle. If you go for the 300, I would think you want to stay with a 1.6 crop for now, and look in to a 7DII when it comes out, assuming it does come out, and is still a 1.6 crop. I still have my 1D4 to complement my 1DX, and a used 1D4 is also something to consider for the needs you have stated. But I think you are on the right track of getting better glass first.




Oct 16, 2012 at 10:08 AM





  Previous versions of Roland W's message #11045565 « long lenses - selecting and buying »

 




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