How to buy a camera lens
An executive summary about buying a camera by Rick Lepage
If you purchased your digital single-lens reflex (DSLR) as part of a kit, you already have a basic lens that takes pretty good pictures. From powerful zooms that get you up close to high-speed lenses that specialize in low-light settings, you have plenty of options for your second lens. While some lenses may go for more than you spent on your camera, you don’t have to pay a lot to get a great lens. Focal Length Technically speaking, a lens’s focal length, represented in millimeters, is the distance between the rear element of the lens and the focal plane, where the parallel beams of light entering a lens converge to a point. This matters to you because the focal length determines the lens’s viewing angle. As a result, a 35mm lens has a field of view equivalent to that of a 52mm lens when placed on the D40.
Aperture The other key component in evaluating a lens is its aperture. Because it collects more light, a lens that opens to a wide aperture lets you maintain faster shutter speeds in low light-this can be essential for obtaining sharp images from a handheld camera. The speed of a lens is described by its maximum aperture. This lens zooms from 55mm, with a maximum aperture of f/4, to 200mm, with a maximum aperture of f/5.6. Keep in mind that faster lenses-lenses with smaller maximum apertures-are generally both heavier and more expensive than slower lenses. Canon lenses with image stabilization have IS in their name, while Nikon uses the term Vibration Reduction, or VR. Of course, you won’t need stabilized lenses if your camera body offers image stabilization. The zoom lens included with many DSLR kits offers a focal length range of 18mm (equivalent to 28mm to 35mm, depending on the camera’s crop factor) to 55mm (equivalent to 80mm to 105mm). When you’re ready to expand, consider investing in a prime lens (which has a single focal length) or a longer zoom lens.
Prime Lenses If you’re looking to develop your compositional skills and get a better lens in the process, I recommend purchasing a prime lens with a focal length between 35mm and 85mm. Prime lenses tend to have better glass in them than comparably priced zoom lenses, and they get you out of the “zoom rut,” where you stand in one place and zoom in or out to fill your frame. Also, most prime lenses have a wider maximum aperture, which makes it easier to get sharp shots under low-light conditions.
These images show the difference a prime lens with a wide aperture can make. The image on the left was taken with Canon’s 24-85mm f/3.5-4.5 lens. The image on the right was taken with Canon’s 85mm f/1.8 prime lens. All of the major camera companies offer good prime lenses from 35mm to 100mm at prices under $500. For Digital Rebel owners looking for a good starter lens, I recommend Canon’s 35mm f/2.0 and 50mm f/1.8. Both lenses offer better low-light performance than the zoom lenses that come in the kits. Zoom Lens If you want to grab action photos, a telephoto lens in the 100mm to 300mm range is your best bet. A 200mm telephoto lens turns into a 300mm lens on a Nikon D40. Likewise, Canon’s 70-300mm f/4-5.6 IS lens-one of my all-time favorites-becomes a 112-480mm zoom on a Canon Digital Rebel XTi. I go to a couple of Web sites for lens reviews. Rentglass.com rents lenses for Canon and Nikon DSLRs on a weekly basis.
