Advantages: Does what it says on the tin Disadvantages: A bit pricey and doesn't work with some lenses
...Overview
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I bought this extender to go with my Canon EF 70-200 f4.0L IS lens. It extends the range to 280mm and increases the maximum aperture to 5.6. This means that autofocus on a 20D, 30D, 40D or 5D body will still function properly ...
Advantages: None Disadvantages: If you want to ruin your photographs buy this converter.
...on the end of my 70-200L f2.8 IS. I would get more use out of this lens than a 100-400 L. In addition due to the f2.8 glass on the lens sticking a Canon 2X would not make a lot of difference and I could live with an f4.8 ...
