This is hard to explain, and it took me a while to find a good website that explains in a way we can all understand.
Nikon cameras come in 2 sensor configurations: Full-Frame and APS-C.
Full Frame cameras are equivalent to the old 35mm cameras.
APS-C are not as good, they take a "picture" of only about 60% of what you are seeing through the viewfinder.
Your camera is an APS-C. Which is also called DX.
Now let us get to lenses. Lenses designated to APS-C cameras are labelled with DX on them. If your current lens is a Nikon it will have a gold DX on it.
A DX lens looks like crap on a Full Frame camera because the lens is too small for the sensor.
But a Full Frame lens with work with an APS-C camera. And it may actually help!
#1. The hardest part to manufacture on a lens is the outside corners. Lenses have to be rounded in such a way that they send the image to your eye that it appears straight, or else you would notice that the picture is wrong. So if you put a Full Frame lens on your APS-C camera, you will only be using the center of the lens! Which is the portion that a lot of people consider to be the best quality section of a lens.
#2. Using a Full Frame lens on an APS-C gives you 1.5 more magnification then the lens specifies! Actually it doesn't, but the camera crops the picture so it looks like a higher magnification. (This is what kritofr was alluding to). This website is the best I've found for explaining the crop factor (
http://www.millhouse.nl/digitalcropfactorframe.html). If nothing else look at the first two pictures, the first one is a Full Frame camera, the second is an APS-C. Both pictures used the same lens and focal distance... but our cameras would be "zoomed in" more. This is why you will see different magnification specifications on some websites (
http://www.londondrugs.com/Nikon%20A...le=Brand%20A-Z - this lens is a 28-300mm for a Full Frame BUT ITS A 42-450mm equivalent on an APS-C).
And now to the downside. Do not but a Full Frame wide-angle lens! Obviously you would be counter-acting the point of a wide angle if the lens "zooms" in more!
And as we have APS-C cameras, we actually need a wider lens then you would need with a Full Frame camera... instead of a 20mm lens, we would need 18mm.
FYI: I own the lens I linked from London Drugs. I like it, it takes great photos, but I'd also like something with even more zoom for really distance animals.