In last week’s post on choosing an SLR, I recommended that you pair your new camera with a 50mm prime lens. A prime lens can be differentiated from a zoom lens in that its focal length is not variable. If you have a 90mm prime lens, all of your shots will be taken at 90mm; if you have an 18-200mm lens, you can shoot at 18mm (wide angle), 200mm (telephoto), and anywhere in between.
Why would you want a prime lens when it so severely limits your versatility? For one, good image quality is much more affordable in a prime lens. It’s difficult to make a lens that has good image quality (IQ) across a wide range of focal lengths, and that’s reflected in the price. Along with that, a prime lens is typically the easiest way to gain the ability to shoot fast. A Nikon D3S will allow you to shoot at ISO 102,400 (you read that right!), but it won’t throw the background behind your subject out of focus like a 50mm f/1.8 lens on a Rebel XSi.
How can you overcome the limitations introduced by a prime lens? Often, you can do it on foot. If you want to zoom in, take a few steps forward; to zoom out, step back (but watch where you’re going!). Your mileage may vary. If you’re in tight quarters, you won’t be able to photograph a group; conversely, if you’re trying to shoot a deer on a hill, you won’t get much detail.
Note that on most SLRs (with a 1.6x crop factor), the 50mm acts like an 80mm lens, which is more of a telephoto. For that reason, it’s especially good for taking pictures of children (active or not) without requiring a flash.