There is some misunderstanding in here, I'll see if I can clear the last bit of doubt from everyone. I'm going to use FX
/DX to describe the formats in shorthand. FX
is a 35mm sensor, DX is an APS-C sized sensor with, in the case of Nikon, a 1.5x crop factor.
People often note the "equivalent" focal length of a lens in 35mm terms - put a 50mm lens on a DX camera and it will have a field of view equivalent to an 80mm lens on an FX
camera. But it is still a 50mm lens. It will have more depth of field than an 80mm lens on the FX
If the pixel density on the two sensors is the same, then the DX camera image will literally be the exact same thing as a crop from the full frame camera. So if you had two cameras with the same pixel density, and the same lens, but one camera had an FX
sensor and the other had a DX sensor, the latter will simply be a crop of the former in appearance. In every way.
In reality, however, FX
cameras tend to have less dense sensors. In the case of the Nikon D700, this is a particularly strong case. At only 12 megapixels, it is much less dense than Nikon's current 14MP lineup of DX cameras.
So if you were to take the same lens and put it on the 12MP D700 and a 14MP D7000, the D7000 image would at small magnifications appear to be the same thing as the cropped D700 image, but due to the much higher pixel density of the D7000, the image on the D7000 would have a lot more detail than the crop from the D700 image.
But if you were to compare the D700 to the D40, the images would be roughly the same (barring noise due to the sensors being much different).
So if you're in an area where you need as much telephoto as possible, having higher pixel density on an FX
sensor will give more detail than having lower pixel density on a crop sensor with the same lens - you'd still need to crop the image from an FX
sensor to match the DX sensor's image appearance. The DX sensor would not be more magnified than the FX
sensor in this case. It would just be a lower resolution, smaller crop of what the FX
sensor is doing.