JeffS, to get a handle on what that means screenwise, I find it useful to know that (with a camera at 0,0,0 pointing up the Z-axis with a zoom of 1) the camera will show 2x2 units at a distance of 1 unit along the Z-axis, and 20x20 units at a distance of 10 units along the Z-axis.
However, if your camera viewport is not square (which it usually isn't...it's usually the proportion of your full screen) the view will be cropped on the shorter dimension. For example, at a typical 640x480 or 800x600 or 1024x768 resolution, which is a 2/1.5 ratio, you'll get 20x15 units showing in your viewport at a distance of 10 units along the Z-axis.
However, if your camera viewport is not square (which it usually isn't...it's usually the proportion of your full screen) the view will be cropped on the shorter dimension. For example, at a typical 640x480 or 800x600 or 1024x768 resolution, which is a 2/1.5 ratio, you'll get 20x15 units showing in your viewport at a distance of 10 units along the Z-axis.