Last week, a friend of mine asked me to help photograph his wedding in Okinawa, Japan. His photographer had to back out at the very last minute, and he needed someone to shoot "a few photos". I'm just an enthusiast and warned him about my lack of experience, but he went ahead and asked me to be the photographer any way.
My setup was the following:
Nikon D7000 with MB-D11 Battery Grip
Nikon D90 with no battery grip
Nikon AF-S 70-200mm f/2.8G VRII
Tamron 17-50mm f/2.8 XR IF (non-VC version)
Tokina 11-17mm f/2.8
Nikon AF-S 35mm f/1.8G
Nikon Ai 50mm f/1.2
Nikon SB-900 strobe (on D7000)
Nikon SB-400 strobe (on D90)
Sandisk Extreme 16GB Class 10 SDHC cards on both bodies
Black Rapid DR-1 Dual Strap
The wedding took place in three different locations - a buddhist cultural center (strong florescent lighting), a hotel ball room (dimly lit to almost pitch dark setting), and to a local bar/restaurant (dimly lit). For the most part of the wedding, the 70-200mm, which I rented, was attached to the D7000, and the Tamron 17-50 was attached to the D90. Occasionally, the other three lens were used to either body (except for the manual-only 50mm which was attached only to the D7000). I occasionally switched the lenses to different bodies to see how each lens performed on both the D7000 and the D90. I took all photos in JPEG Fine.
While I did not conduct a scientific experiment, I must say that I was impressed by both the D90, which I have used for the past two years, and my new D7000, which I've had for only a week. On the 70-200mm, Tamron 17-50mm, and the Tokina 11-16mm, I found that the D7000 autofocused faster and more accurately, especially in dim light. Especially on the Tamron, I found that the D90 sometimes had to hunt for the subject in low light.
The D7000 also had very noticeable advantage over the D90 in the frame rate per second. Not only is the FPS faster, but the buffer seems much larger, allowing to take continuous high frame rates over a longer period of time. At one point, using the same lens and same settings, I counted about 22 continuous frames on the D7000, while the D90 could only handle about 6 frames before slowing down.
As many in this forum have already noted, the D7000 does have very good low-light capabilities. When I only had the D90, I was often afraid to take it above ISO 800 for really high quality, noise-free photos. With the D7000, shooting at ISO 1600 produced very high quality photos with little noise increase from ISO 800.
I also found the MB-D11 battery grip invaluable when shooting with a heavy lens like the 70-200mm. In fact, since I returned my lens, I've kept the MB-D11 attached, just because of the high quality feel of the rubber in the grip, which feels more like holding a D3/D700/D300 than a D90/D5000/D3000 series. To be honest, without the battery grip, the D7000 does not feel that different at all from the D90. The D7000 may have a slightly more rubbery feel, but nothing compared to its higher-end siblings. The grip definitely adds a professional feel when holding the camera. Despite this, parts of the grip, especially the lever that opens the battery compartment feels extremely plasticy.
I did have several problems with the D7000. First, the autofocus would sometimes stop working. I would have to turn the camera off, and take the lens off and mount it back on for the the AF to work again. This happened several times during the wedding that led me to miss several key shots.
I also found the command dial on the top of the camera to change the Manual, Aperture, Shutter, Program, Scene, etc, would accidentally move around during shooting. This may not be a problem for casual shooting. But using the Black Rapid DR-1 dual strap, I found that the camera would often bump into my body or something else and accidentally move the dial to a different setting. The D90's command dial seems to be a bit tighter to move, and I did not encounter this problem at all.
In addition, I found that the SD card slot door often opened accidentally as I was grabbing the camera to shoot. Because the memory card slot door on the D7000 is twice as long as the D90, sliding my hand into the grip of the D7000 often caused the door to accidentally open, which often slowed me down. Again, this should't be a problem for most D7000 shooters, but it gets in the way if you need to shoot something immediately.
Overall, from a non-professional photographer's perspective, the D7000 is an excellent DX camera that is a great improvement over the D90. If DX can be this good, I truly would look forward to what the future of FX will be like. I also wonder what will happen to the D300s, which is now selling at a lower price than the D7000 in Japan. The venerable D90 worked as expected, and I find that in well-lighted conditions, there really wasn't a huge difference in photo quality between the two cameras (again from a non-professional perspective).
While it's not directly related to either camera, I found the 70-200mm to be a invaluable asset when shooting weddings. I've used the 55-700VR and the 18-200 VR before. Neither of these lenses compare to the sharpness and the low-light capabilities of the 70-200mm VRII. If I had $2000 more, I may look into buying this amazing lens. That said, I found that when using it with the Black Rapid strap, the lens would bang against my legs or my waist, causing the VR and AF switches to accidentally move. I sometimes found myself shooting with the VR accidentally turned off.
I was very disappointed in the SB-900 speedlight. While I worked with Panasonic EVOLTA alkaline batteries and no external power source, the strobe would overheat every 5 to 10 minutes. The EVOLTA batteries lasted about an hour per set, and the batteries seemed so hot when they were taken out to be replaced, I actually thought they would explode or melt.
The SB-400 on the other hand worked well, though its low guide number was no match for lighting subjects far away. That said, it never overheated, and the battery was never replaced during the five hour shoot.