I'm very new to shooting sports but I'm looking for some opinions on some examples of shots with my 70-200 2.8IS and Kenko 1.4x. I've been debating picking up a 300mm f/4 but I'm undecided. These shots have significant cropping and were shot using a monopod. I'm sure I'd pull out better DOF and more sharpness with a 300 2.8 but it was worth a try.
5D MK II with 70-200mm f/2.8IS + Kenko 1.4x shot at 280mm
ISO 100, F/4, 1/2500, lots of cropping
40D, 70-200 2.8IS + Kenko 1.4x
ISO 600, F/4, 1/1600



But both do look acceptably sharp even with cropping. On the second shot I would have positioned my self so the sun was at my back.
