Biggest, in terms of money involved, piece of equipment is a nice piece of glass to put in front of our camera.
Since my wife had been using a Canon SLR since forever (and we stayed with that when moving from the EOS 300 to the current EOS 40D), the choices to upgrade from the kit EF-S 17-85mm f/4-5.6 basically have been:
- EF-S 15-85mm f/3.5-5.6 IS USM: since it's been announced with the 18Mp 7D it should be quite good on the 10Mp 40D. Newest design, certainly one of the best IS on Canon, true wide angle.
- EF 24-70mm f/2.8 L USM: The old trusted one. No IS, but a constant f/2.8. Narrowest zoom range of the lot. A real tank, at almost 1kg.
- EF 24-105mm f/4 L IS USM: The other full frame L lens. Not quite as big, longer, but only f/4.
- EF 24-70mm f/2.8 L IS USM: including waiting for it to be announced and available, of course.
In the end I got the EF 24-70mm f/2.8 L USM, because the EOS 40D is no high ISO monster (we don't plan to upgrade immediately.) Also: I bought the Tokina AT-X 116 PRO DX (11-16mm, f/2.8) a while back and we're quite happy with that so wide-angle is covered. And since we're often shooting indoors (family and other events), f/2.8 is a big plus. On the tele end, there's quite a gap from the 24-70 to the old EF 100-300mm f/4.5-5.6 USM [age of the page to reflect the age of the lens ;-) ] but then the latter is probably the next lens to be replaced anyway.
Since I only got 24-70 I can not directly compare these lenses. But after a few early tests I think I'm happy with the 24-70: while it seems to be a bit soft wide open at 24mm and at 70mm, it seems to be very sharp center to edge even at f/2.8 when used in the 35-50mm range. (Note that the 40D is a crop sensor camera, so I'm nicely using the sharp “center” area of a lens designed for full frame!) Yes, it's huge, so for casual walking around the 17-85mm will probably still get some use. Time will tell. And since it can, potentially at least, be used on a a EOS 5D Mk II, I now have another gadget to covet. Although this would mean giving up the Tokina 11-16mm. Anyway, not for quite some time yet...
(The test also included the venerable EF 50mm f/1.8, Mk I, and I must say I'm quite surprised how sharp that one is in the f/4 to f/11 range.)
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