70-200 f2.8L, (145mm f3.5, 1/500 sec., ISO 200)
One other consideration depending on the camera you are using, you will need a lens with a maximum aperture of f2.8 or faster in order for the high precision focus points to work. On the 10D, D60, D30 and the Digital Rebel models there are no high precision focus points, but the higher end Canons have high precision focus points which only operate in high precision mode with lenses which have a maximum aperture of f2.8 or faster. High precision focus means the auto focus locks within 1/3 of the depth of field, normal precision focus points lock the focus within the depth of field.
Another consideration is that some autofocus points (other than the center point) are less effective with apertures slower than 4.0. While the 70-200 f4.0L is within this range, if you add the 1.4 extender the maximum f stop jumps to f5.6 (you lose one stop with the extender). Personally I use the 70-200 2.8L (no IS) and have found this lens to be a terrific value. With the 1.4 extender, you wind up with 100-300 f4.0 as well as a 70-200 f2.8, one very useful lens.
IS is a big deal, but often not mentioned is that the amazing low noise characteristics of the newer Canon EOS digital SLR's means that you can buy back shutter speed by increasing the ISO in lower light situations rather than worrying about lenses with IS (which by the way, only helps with camera shake, not subject movement, something often overlooked). The 70-200 f4.0L zoom is a great lens, but for a few hundred bucks more you can get the 70-200 2.8L without IS, and depending on your shooting style this lens may ultimately be the better value. (It also ships with the tripod collar at no additional charge).
For more information on the Canon high precision auto focus system, there is a detailed discussion by Chuck Westfall (Canon USA) on this website:
http://www.bobatkins.com/photography...q/eos3af.html. While it was written about the auto focus system in the EOS 3 film camera, the specifics are applicable to all higher end Canon cameras. Note the table relating to lenses, extenders, and high precision auto focus.
I am a bit of a grinch concerning Canon zooms, for a lot of reasons (mostly involving the speed and accuracy of the auto focus system) I think you are better with the Canon zooms rather than other brands.
John
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John Fisher
Couture Model Management
900 West Avenue, Suite 423
Miami Beach, Florida 33139
305 534-9322
http://www.johnfisher.com
http://www.couturemiami.com