My first 70-200mm Llens was the f4 IS. I still have it. I have bought 4 of the 70-200 F2.8 lenses (1 was non IS) when they showed up on our local craigslist for too low of a price. Their sharpness was pretty much equal to the F4 at the same aperture, but slightly softer at larger apertures and at 200mm.


I sold all 4 merely because they were too heavy, and the one time I was in a low light situation, they did not have a wide enough aperture. I use the f4 and carry it with me, and use a prime for low light. My 135mm L is a favorite with my 5D MK II, with the 85mm 1.8 and 50mm 1.4 are close behind.


I'd like to get a long lens with short mfd that is sharp enough to work with a teleconverter on my 1D MK III. I did once have a 400mm F:/5.6, but without IS, I needed a fast shutter speed which limited me toexcellent lit scenes, and the mfd was too long.


I like the 300mm 2.8 and the 100-400 L, but I sold my 100-400mm L four years ago when I was justgetting started because I could not master the push-pull. I'm holding off until later this spring to see if anything new comes out, the Sigma 50-500 OS sounds interesting, but the MTF curves really do not look impressive at 500mm.