'chelle types faster than me! Of course we won't laugh. But a trip for you to the library may be in order. The focal length of the lens determines perspective. And yes, the 50mm of a "normal" lens should provide the same perspective as your 10-70mm zoom set at 50. However, a fixed focal lens, sometimes called a "prime", may offer some advantages over using the zoom. It may provide sharper results, or the lens may focus closer, or take in more light (f-number smaller). What lens you use really depends on the type of photography you want to do. The 18-70mm offers a pretty nice range for general photography. [The D70 is a digital, right?] If you lean more towards wildlife or sports, a longer lens, maybe a 200mm, or one of the zooms that go out this far, may be an interesting choice. If you do more people/street photography, a wider lens, maybe a bit faster, is suggested. [Though at 18 with your present zoom you are already pretty wide. The smaller the f-number the "faster" the lens, or the better it is for photographing in low light levels. The smaller the f-number, the bigger diameter of the lens. So it is heavier and costs more. Most of the time really fast lenses aren't needed, but in dim light they can be the only way to make the shot. For general use, around F/2 to 3.5 for medium to short telephoto is usually cost effective. For a 200mm, f/4 to 5.6 is pretty reasonable. A 500mm mirror lens is kind of a special purpose beast. They tend to be quite slow, f/8. I use mine occasionally, but not more than once or twice a year. Considering what you already have, I'd bet that one of the newer not-terribly-pricy 70-300mm f/4 to 5.6 compact zooms would be a good bet. As in most things in life, you do get what you pay for. You can find a pricier lens which is perhaps "better", but these are darn nice! Generally you can fond comparative reviews of lenses in the photography magazines, or by Googling.