2x extender III any recommendation yet

[stephan_matthies]

<p>Hi there,<br>

does anyone have experience yet with the new 2x extender iii, specifically in regard to possible combinations with tele lenses? How is the IQ loss in comparison with the 1.4 extender? Does it maintain the AF-possibility f.e. with the 100-400 mm lens? Thanks in advance.<br>

Stephan</p>

[steven_crist]

<p>I don't have experience with the model III extender, but typically the model II 2X gave poor results with anything less than the super-telephotos (300 2.8, 400 2.8, 500 4, 600 4). If you're using it specifically with the 100-400 it will certainly get you closer views, but you'll pay a price quality wise - not terrible, just noticible. I have the 100-400 and use it with the 1.4 tc and it gives OK results. You will loose AF with the 2X and 100-400 combination. </p>

[steve_dunn2]

<p>I haven't been looking, so I may have overlooked something, but I don't recall having seen any formal test results or user reviews of the III. For what it's worth, I'm sure you're aware that Canon claims its optics are a significant improvement over the earlier 2x models. Also, the optical performance of a lens+TC often improves at least somewhat if you stop down a bit; the problem here is that even wide open, you're at f/11 with an f/5.6 lens and a 2x TC, so stopping down to f/16 or f/22 may simply not be practical in many cases.</p>

 

<p>There is no change to the body's requirements for autofocus. Many EOS bodies require that the lens (or lens+TC combination) be f/5.6 or faster in order for AF to work. Some bodies have one or more autofocus points that will work with a lens (or lens+TC) as slow as f/8. No EOS body is designed to maintain autofocus with a lens any slower than f/8. With the two-stop loss of a 2x TC, you'll lose AF on most EOS bodies unless the lens (without the TC) is at least f/2.8, and no EOS body will retain autofocus if the lens (without the TC) is slower than f/4.</p>

[Robin Smith]

<p>My scepticism is such that I doubt the ver III will be any improvement over the II for most lenses. I reckon the new teleconverters were introduced solely to work well with the newly-designed superteles introduced earlier in the year where the older TCs were not a good match. I think the end result will be unchanged when using the ver III with any of the original set of lenses for which the ver II was designed (i.e. 70-200mm IS f4).</p>