Dimensions: The D70 measures 5.5" x 4.4" x 3.1", while the D80's dimensions are a more compact 5.2" x 4.1" x 3.0". Each weighs 1.3 lbs.
LCD size: The D70's LCD is 2", with a pixel TFT of 130,000. The D80 has a 2.5" LCD screen, 230,000-pixel TFT, and includes a protective cover for the screen. TFT means "thin film transistor" and refers to the resolution of the screen; TFT is the most advanced, and expensive, flat-screen technology available.
A camera's resolution, measured in megapixels, determines its ability to capture image details. The D70 is 6.1 mgp; the D80 is a 10.2 mgp camera.
Because of this difference, the D70 image sizes are 3008 x 2000 pixels (largest) and 1504 x 1000 (smallest). In comparison, the D80 can produce a large image size of 3872 by 2592 pixels; the smallest is 1936 by 1296.
Bigger doesn't always mean better: It depends on what you want to end up with. If you want to store as many photos as possible, for instance, if you are in a situation where you are unable to download quickly, you should choose the smallest size image setting. If you want to make large prints and crop your photos, you'll want to choose the largest image setting available.
Both models are considered "continuous" because they can shoot three frames per second. This is important if you want to take shots in rapid succession and can't wait for the annoying pause while the shutter resets.
Both cameras are comfortable and easy to use because of their ergonomically placed controls.
Although many camera buffs consider the D70 to be a near-perfect camera, the D80 does offer some changes and improvements to some of its functions (not necessarily enough to make loyal D70 owners want to switch to the newer model, however):
On the D70, the diopter control is a vertical slider located behind the rubber eyepiece of the viewfinder, which means removing the eyepiece to make adjustments. The D80's diopter control is in a more convenient location.
While the viewfinder frame focus is 95% on both models, the D70 offers .75x
magnification, and the D80, .94x.
The D80 offers exposure delay and multiple exposures; the D70 offers neither.
Unlike the D70, the D80 has wireless capability for cable-free photo transfer
Unlike the D70, the D80 can accept a vertical grip, which is an extra battery pack that attaches to the camera. It offers added stability in camera handling and frees you from continually worrying about how much power you have left when you're in a pinch.
The D80 enables in-camera retouching, including red-eye reduction, monochrome and filter, trimming, small picture and overlay. The D70 does not offer in-camera retouching.
Camera prices depend on what is included with the purchase, for example, lenses, a carrying case, remote control and USB cables; and where you buy it.
A new Nikon D80 ranges from about $1,000 up to about $1,500; the Nikon D70, anywhere from $1,700 to $2,400.