Thinking of getting an extender...

[BiikeMike]

I've got a 70-200 f/4, and thinking of getting an extender. What do they do to the aperture and autofocus?

I'm still kinda new to this whole thing :)

[winkie]

http://photography-on-the.net/forum/showthread.php?t=41922

[calicokat]

A 1.4x extender is going to give you a focal length 98-280 and an apeture of F/5.6. You can still autofocus on all Canon bodies. 2x extender gives you 140-400 with F/8.0. Only 1 series bodies are going to allow autofocus.

[morehtml]

On that lens you are at most going to want the 1.4XTC. The 2XTC is going to lose your autofocus unless you have a 1 series camera and the 2X will probably degrade image quality more than you want on that lens.