Quote Originally Posted by RazorTM
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Thanks for the comments and welcomes, all. I think that the 300 2.8 IS is not bad at all on the autofocus side, but the image quality takes a huge hit when combined with the 2x II. CA, distortion, sharpness, and contrast are all fairly bad. Here's a 100% crop of the egret's head. There's barely any detail in the feathers, and this is absolutely as sharp as I can get the images before they look oversharpened but still not very sharp:



Also, this was shot at f/8. The combo is best at f/11, but the 500 f/4L IS is even sharper at f/4, wide open.
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It's not that bad for a 2x. Doing a 100% crop on top of a 2x, making your a 300mm a 1200mm and expecting to see a lot of good IQ would really be a stretch. For me the 2x IQ on any lens isn't good enough, but its as good as it gets on any lens with the 300mm 2.8L.


It would be a better comparison for the 1.4x on the 300mm 2.8L for 420mm to compare it to the 500mm F4L bare. With the 300mm and the 1.4x the images are quit good. I find it very acceptable. Of course the naked 500mm will be just slightly better against the 300mm with an extender. Really, IMO I think mine puts out better IQ than the 300mm with no extender but not by much. I am going to upgrade to the II version when it comes out. Even if the IQ is equal (which I believe it will be noticably superior)I think the weight savings is a big plus. I just haven't decided on the 500mm or 600mm yet.