"However, what annoys me is the fact that the better, more sensitive focussing of the 40D does not enable one to autofocus at f8 as the 1 series cameras can. If it did, I would consider that a real plus factor. I could then use my 100-400 IS with 1.4x extender, get the benefit of extra telephoto reach (compared with my 5D) as well as autofocussing capability.
When I upgrade a camera, I want to see some positive, definite, fundamental and clearly defined improvement that I know I'm going to find useful in a real sense, like "if only I had a 40D I could have got that shot". I'm not particularly motivated by wish-washy, feel-good ergonomic factors in themselves, although of course I'd rather have them than not." --Ray
I need positive, definite, fundamental...improvement. Me, too, and the 40 is all of that. There have been multiple in-depth reviews on the net of the 40d by credible experts not just guys taking pictures of their cats (or, when I clicked on a link of someone who was slamming the 40d--but of course, had never seen one--as being inferior to the as-yet unreleased d300, I found that the example of his own work he was so proud of was a poorly composed group grip-and-grin shot of guys with dead fish.). They've concluded that the 40d is very, very close to the 5d in IQ. FWIW.
I just returned from Africa (second trip to Zambia in a year), and I can tell you I did get "that shot" and hundreds more with the 40d that I didn't get--couldn't get--last year with film. For my "long" lens I used a f/4 300L IS with 1.4 tc, and I was able to focus on pretty incredible night time predator/prey/predator--long story--interactions at night under only a spotlight.
I'm a digital SLR newbie having switched from EOS 3's which I used last year, with the same lenses (T-90's and F1n's before that), to digital for the first time, so can't comment on whether the 5d or 30d, 400d or d300, or..., would have focused under similar low light conditions, but I can tell you first hand my EOS's never would have been able to. Of course the shots would have been impossible anyway because of film ISO limitations. There may "only" be 9 sensors, but Canon did something amazing to get those things to lock on in low light and in spite of foreground clutter (like branches).
As for the 100-400, lots of safari-goers--even pro's--love it, and I did do quite a bit of lens switching with my fixed focal length, so a long zoom would be attractive. But, with the 1.6 crop combined with the 420 mm total focal length, I had plenty of reach--and good enough quality on many shots that I could even do some judicious cropping and still have a really nice, sharp image.
And, yes, I was very happy for the in-sensor cleaning (It works!). In fact, that's a major reason I waited for the 40d.
I should think that the 5d and 100-400 mm without a tc should produce really nice images that could handle cropping. And, that's the difference between getting a shot that might not be perfect but plenty good vs. no shot if you can't get focus on a rapidly changing scene.
I was going to buy an EF-S wide angle lens for the 40d (my widest is 20mm, because I do like to do wide angle, close focus landscapes, but I've decided to hold out for the 5d follow-on, which I'll bet has sensor cleaning (I really do not like the idea of mucking around inside my camera to clean the sensor). So, I'll have the best of both worlds, IMO, when I go back to Africa (and Alaska, and...) next year. One thing I do miss in the 40d is the lack multi-spot metering. I loved being able to keep my eye to the viewfinder and average several spots around a scene to get the exact exposure effect I wanted. Just the way I got used to shooting with my beloved t90.
I'm brand new to the forum, but when I have a chance I'll provide a link to a few pix. BTW, I LOVE IS. Cannot believe how sharp my pix are (when I do my end of the job right), even handholding in a canoe. And, I'm a guy who alway shot transparancy film, Velvia 50/100--rarely 200--and, going way back, Koda 64. exclusively).