Delija wrote in post #13980850
Not sure why you seem to have a problem with using a 1.6x crop camera like your T2i - As was mentioned, along with the 1D cameras, the crop 7D has a very advanced focusing system - I haven't used a 1D3, but my guess is that the 7D would be in the same league as that camera for focusing tricky (fast moving) subjects like "Eagles in flight" - (maybe better
).
As for comparing the 1D3 to the 1D4, the 1D4 is much newer technology and has both substantially greater resolution as well as far better high ISO performance.
I don't think anyone would be surprised that your 5D2 isn't working well for you with it's focusing system. It's a great camera with great image quality, but for following fast moving objects, that is probably it's weakest practical use.
Since money doesn't seem to be a factor to you, and since you seem to be dismissive of "crop" sensor cameras - my guess is as a self proclaimed "newby" to digital photography, this could easily be from reading too much from those who think that what they refer to as "full frame" is some kind of magic. In reality, 35mm film cameras were always considered a compact format - just movie film turned on it's side. The only smaller (professionally used) film format was 16mm motion picture film- used in close to 100% of wildlife documentaries.
Specialty stuff like 11x8mm film for Minox "spy" cameras aside - for still photography, other than the short lived and failed experiment with APS film cameras - as far as I can remember, 35mm was and always has been the smallest commonly used film.
BTW, 35mm cameras used to be called ''miniature cameras" - (maybe that term went out of use when the Minox got popular - but 'miniature" is what 35mm cameras were known as).
But since you seem to have a problem with a 1.6x crop sensor camera - even made mention of the 1D4 being a 1.3x "crop" camera, which seems to be a problem in your estimation, I guess if I were you I'd just do the common sense thing and hold off and buy the 1DX when it becomes available. It will do everything you want - be perfectly suited to every use you listed and not "drag you down" to the 1.3 crop factor of the otherwise excellent 1D4.
All the rumors about the so far non-existent 5D3 having an advanced focusing system like that of the 7D and a frame rate of about 7FPS - I have to believe that's wishful thinking at best.
The 5D is what it is - not a camera for sports or for wildlife - It's always been all about great "image quality' - The ideal camera for portraits and landscapes - (maybe the new version will come in a kit with a tripod instead of a lens) -
- The 5D cameras (and I own one) is also a good choice for photojournalists who have no desire to carry a 1D size camera (or two). Smaller, lighter and relatively unobtrusive (or at least "unobtrusive" until virtually every 5D owner that is new to photography feels adding a grip makes them look more "professional") - LOL
Meanwhile it took me about 10 seconds looking in the "Birds" sub-forum on this website to find these shots of eagles in flight taken by POTN member "SteveJA" - with a "lowly" 1.6x crop 7D.
Link at bottom of this post:Since the EXIF info shows 700mm, I'd have to guess he used a 500mm lens with a 1.4x extender. (really with a 35mm field of view of an 1120mm lens when taking the 1.6x crop factor into consideration - something a lot of people see as a benefit).
Certainly a lot more difficult lens to keep on focus than a 400mm lens on a 5D. Guess the focusing system on the 7D is more useful (for this purpose) than a "full frame" sensor with what is essentially one usable focus point. It isn't the lens that struggled for you to get on focus, as you seemed to imply (hard to tell from your wording if it was the lens or the 5D2 that you felt "struggled") - but either way, it was the focusing system of the 5D2 - great for portraits, landscapes, dog shows - etc. Not so great for fast moving objects.
https://photography-on-the.net …/showthread.php?t=1154347 
