I haven't personally used the Nikon D700 but my strong impression based on reading infinite reviews online and descriptions of its features, along with looking at individual photos, is that it is easily the best camera out there below $6K (Nikon's pro cameras and the flawed-but-still-compelling Leica M9 would give it stiff competition beyond that line). Reports are coming in aplenty that stocks of the D700 are low, signaling a replacement may be around the corner.
If this is so, I hope that Nikon keeps the features that make the D700 so marvelous (fast focus, incredible high ISO ability) while adding a few enhancements (video, mild megapixel upgrade). If Nikon makes the camera I think they're going to make, it could be a real dream. My only hesitation on the D700 is the megapixel count. Though 12 megapixels is more than enough for portraits (in my estimation), I've got some reservations about losing the ability to make significant crops on the telephoto end. I'm not very greedy when it comes to megapixels, 18-20 on a full-frame sensor would be fine.
I've been a lifelong Canon user but I've been eyeing the other side for awhile now and I believe I may have to make the jump, as much of a pain the ass it is going to be unloading Canon gear, or at least duplicating it.
It's really just basic features that tick me off about Canon. Why can't Canon make a working Auto ISO? The Auto ISO on Canon cameras SUCKS. First, it will only default to 400 on flash, regardless of the flash setting. Second, it usually hovers around 400-800, regardless of conditions- meaning if I have an IS lens attached to the camera, it ends up shooting at 1/20 shutter speeds, far too slow to capture any person not encased in wax. There is no way to control maximum or minimum shutter speed on Auto ISO or to reliably use it in semi-dark conditions (late afternoons/early dusk would actually be the times when Auto ISO would be most useful).
Because I can't use Auto ISO on my Canons, I find that it is that much harder to use manual exposure. When photographing under changing lighting conditions, I would prefer to set the aperture and shutter speed myself and let the ISO be the variable, but the camera doesn't give me that option.
Another letdown with Canon is the viewfinders (this has more to do with my 40D and 7D than its full-frame cameras). As far as I know, Canon offers the worst APS-C viewfinder contrast-level of any camera company.
Thus, I have a semi-pro 7D with a $1,700 list price (of course I paid much less) and I can't manually focus because the viewfinder won't even read apertures wider than f/2.8. I'm not looking to manually focus at f/8 or f/11. I want to be able to manually focus my Sigma 30mm f/1.4 in low light, where it has terrible autofocus.
This would seem like an obvious feature for camera designers to include (and indeed, even Canon includes EF-S screen options for its 1D and 5D cameras). Somehow, the 7D engineers missed it, not even providing the option of earlier Canon cameras for an add-on screen replacement. The only option I have on my 7D for wide aperture autofocus is live view, which still has mechanics that are pretty clunky at this stage. Suffice it to say that while live view might work for a slow portrait, you're not going to be catching any kind of live action well by manually focusing live view on a 7D.
An alternative choice used by many APS snappers is buying one of the Katz Eye installations, which would end up coming to a few hundred extra dollars in cost (split prism + optibright + labor). If I keep the 7D, I will probably end up doing this, but it is a bit infuriating to have to spend $200 or more on a basic feature- one that should have been included in the camera to begin with.
The lack of a focus assist light in Canon SLRs is also bothersome- even cheap crappy point-and-shoot cameras come with focus assist lights included. Canon's retort (as I've read online) is that users can use the flash as a focus assist mechanism.
No, not really. If you want to use the in-camera assist light in lieu of a designated focus assist light, the built-in flash sends off a rapid series of power strobes. Aside from drawing a lot of unwanted attention- maybe you just wanted to be the fly on the wall photographer and not the disco light system?- the built in flash strobes are remarkably slow at arranging focus. The focus assist on the overhead flash works a little bit better, sending out a quick red stream, but that only works if A) you are using flash, and B) the flash is pointed in the direction of the subject (as opposed to being used as a side flash or bounce).
Finally, and most relevant (i.e., the biggest straw on this camel's back):
The dead autofocus of the 5D Mark II. Based on all reports I've heard or read, the autofocus in the 5D is terrible, a 9-point leftover-from-the-30D focus plan intended to cover a full frame sensor. Canon was obviously saving its real focus for the 1D (45-point autofocus capability has been in Canon's hands forever, going back into the film age).
While I am sure the upcoming 5D Mark III will include better autofocus than it's predecessor's (maybe in line with the 7D's), I'm not sure that it will match Nikon's prospective D800 (or whatever the D700 replacement ends up being called, Nikon naming can be a bit erratic). Nikon has 51-point autofocus in the D700.
Furthermore, even if the 5D III is better at autofocus than the current Canon 5D, it will probably be handicapped by other issues, including 1) Basic mechanical flaws such as the ones I mentioned (lack of functioning Auto ISO and/or focus assist light, etc.), and 2) Too many megapixels. If the sensor is pushed toward 30 megapixels or above, image quality will go down with it.
Canon jumped from the 13-megapixel 5D to the 21-megapixel 5D II with only a slight hit in IQ (and a boost in it at the high ISO end), but I have a feeling megapixel expansion won't be as simple the next time around. Canon has already demonstrated with the 7D/60D/600D how many megapixels they're willing to pack onto a sensor- more than they need.
The 7D is a pretty good camera, but it would have been a lot better if it had been left with an improved 15 megapixel sensor- fewer artifacts, less diffraction, better noise control, etc.
For the reasons above, I'm leaning toward Nikon, though Canon offers the best lens stable on the market (those lower-price-than-Nikon 100mm and 135mm primes and 70-200 f/4L's are nice). This isn't the film era; the camera bodies themselves are a far larger ingredient than they used to be.
To Canon's credit, I will say the 7D was a huge leap over all previous APS-C cameras, including the 50D and the Nikon D300, when it was released two years ago. The 7D has a few things I like: 1) great shape in the hand, 2) a just-bordering-on-100% viewfinder, 3) spot-on focus (focus accuracy is way beyond xxD land), 4) significantly better exposure control in outdoor light than the 40D (but indoor exposure can still be a little uneven), and 5) a lightning fast frame rate (I rarely need 8 fps but it's nice to have to catch acrobat flying through the air).
I love my 7D, but at the end of the day it doesn't the image quality I want or need at high ISO (3200 and especially 6400). If I mostly shot outdoors, this wouldn't be a big deal, but I do a lot of low-light photography. It's a damn shame. Sensors are improving every year, but they're not improving that quickly. The Nikon D7000 and Pentax K-5 set new marks for APS-C sensors, but they still can't match the sharpness of the six-year-old Canon 5D Mark I and its full-frame capture (they do surprass some of the earliest APS-H cameras, in my estimation).
When trying to judge camera quality, there is still one easy critera: sensor size.
The best 1/2.33 camera is worse than the worst 1/1.63. The best 1/1.63 is worse than the noisiest micro four-thirds body. The best micro four-thirds body is worse than the noisiest APS-C camera (on the market today, I'm not talking about legacy cameras).
I can't find any exception to this sensor-size-denotes-quality rule... until you get to the Sony a850.
Yes, sadly, Sony's prosumer-line full-frame camera is a piece of crap and its high ISO performance lags behind some of the better crop cameras. Anyway, the a850 has been hovering on the to-be-discontinued watch list since just after it was released and all signs signal that it is finally nearing the exit.
Goodbye Sony a850, hello Nikon D800. That's a marketplace trade I'm willing to make.
Feb. 27 Update: One issue I forgot to mention in the whole Nikon vs. Canon debate is lens compatibility. Thus cuts both ways. While it's convenient to be able to use old Nikon manual lenses on new Nikon bodies, this has also meant that it has been more difficult for Nikon to develop video (one reason why Nikon's capabilities are behind Canon's in this regard). Newer Nikon entry-level cameras (e.g. D3000, D5000) don't have compatibility with older Nikon autofocus lenses, including many autofocus primes.
Old Nikons lenses- but not old Canon FD ones- can be attached to Canon DSLRs via adapter. I bought several Nikon lenses for use on my 40D and only belatedly realized the viewfinder was so bad that attaching them was useless.
Personally, since I don't have much present use for either video or entry-level bodies, the Nikon would make more sense for me... I do have a large interest in old manual lenses, especially with fast (f/1.4) apertures.
A new rumor.