The marketing point is pixels. Camera companies traditionally have sold cameras based on megapixels…more = better, they imply. In reality, it’s the quality of the megapixels that matters, and that largely translates to the size of the photosites. It’s the reason that a 12 megapixel FX camera like the D3/D700 blows away all the DX cameras in terms of image quality, color and ISO…bigger photosites because it’s the same number of pixels on a much bigger sensor. The problem is that full-frame sensors are really expensive, and it’s just harder to sell pro-level $5000 cameras. DX camera are just cheaper.
Because a lens essentially crops the center out of the DX sensor, that crop factor has to be accounted for. The result is that a 50mm lens on a DX sensor actually performs as if it were a 75mm lens (Nikon uses a 1.5x crop factor), whereas on a full frame dSLR, or a 35mm SLR, a 50mm lens acts like a 50mm lens.
Simply put, a 50mm on DX looks like a 75mm on FX. 35mm lens on an FX camera requires a 24mm on DX to get the same field of view. A 300mm on FX looks like a 200mm on DX. So on the long end, you can get a little more reach for your dollar with DX. However, if you like to shoot wide angle, it’s a bit harder to do on DX. Nikon’s 14-24mm wide zoom isn’t near as wide on DX. You’d need something like 9mm to get the same FOV. Something like a 70-300mm is a far-reaching SOB on DX, though.
I’ve had two D3’s, a D300 backup and 6 of the Nikkor lenses. I’ve also had the Canon 1Ds Mark II and 1D Mark III along with the 5D and 30D with a number of L lenses…. then there was the Leica film cameras about 8 years ago.
If I was buying something now just to have around, I’d pick up a D700s, used if I could find it. The D700 would be good too, but the “s” has the HD video feature and better ISO sensitivity.
As for lenses, I’d be happy with the 50mm 1.4 and a good longer lens.
The D90 would be an ok choice as well as it has the video feature, but the body is small compared to the full frame sensor bodies…
