| Author | Thread | 
		
			|  | 11/22/2007 08:55:48 PM · #1 | 
		| | What are the pros and cons?  I will be using mainly with a 300 4.0L IS and 70-200 2.8L IS.  Which do I want? | 
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			|  | 11/22/2007 09:02:26 PM · #2 | 
		| | Depends on how much reach you need. The 2x on the 300 f/4 probably won't autofocus, not letting in enough light. The 1.4x is, I believe, a little sharper. I had one, actually, but I took it back. I was using it on the 70-200 f/4, and not getting much use at all out of it. 
 1.4 will turn your 300 into a 420. Then with the 1.6 crop factor, that's the equivalent of what, 650mm on a full frame sensor? The 300 will autofocus with the 1.4...
 
 R.
 
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			|  | 11/22/2007 09:02:35 PM · #3 | 
		| | The 2.0x with the 70-200 will need to be stopped down 2 stops (f/11) to recover sharpness. It will be pretty soft wide open (f/5.6). The 300/4 with the 2.0x will not AF except with 1-series bodies (max aperture is smaller than f/5.6). You're going to be more satisfied, IMO, with the 1.4x. You only lose a stop instead of 2 stops, and you lose less sharpness, plus your 300/4 will AF with your body.
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			|  | 11/22/2007 09:53:35 PM · #4 | 
		| | I've been very happy with the 2x - I've had some pretty decent results with it on the 70-200 2.8L IS. 
 It seems to retain it's sharpness (although I've read a LOT of poor reviews on it).  The only issue I've seen is it can definitely produce some strange bokeh effects.
 
 Exhibit A:  this shot at 400mm f/5.6 iso100 (the 70-200 with the 2x)
 
 
   
 definitely still sharp - but strange background.
 
 Message edited by author 2007-11-23 01:25:21.
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			|  | 11/22/2007 11:31:41 PM · #5 | 
		| | the 2x if it is reach you are after get reach
 I shoot the 2x with the 500 L f4 and still have plenty of light
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			|  | 11/23/2007 12:04:10 AM · #6 | 
		| | Just to be clear: a 1.4x teleconverter will make your max. aperture one stop smaller, and a 2x teleconverter will make the max. aperture 2 stops smaller.  So on your 70-200, that means 2.8 becomes 4.0 and 5.6, respectively. | 
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			|  | 11/23/2007 01:25:44 AM · #7 | 
		| | I think they are pretty much saying go with the 1.4 :-) 
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			|  | 11/23/2007 02:21:49 AM · #8 | 
		| | I have a 2x that I use with a Canon EF 100-400mm f/4.5-5.6L IS.  At 800mm not having auto focus was a real disappointment with my 20D.  Everything got much easier with the 40D and live view. | 
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			|  | 11/23/2007 02:08:05 PM · #9 | 
		| | | Originally posted by fotomann_forever: I think they are pretty much saying go with the 1.4 :-)
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 Not necessarily...  I love my 2x, and it'll definitely be staying in my bag  :O)
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