Before you can choose between these two types of lenses, you have to understand the difference.
Simply put, prime lenses are lenses with a single focal length. Prime lenses come in a large number focal lengths ranging from wide angle through super telephoto.
Zoom lenses are lenses which have a variety of focal lengths within just one lens. Zoom lenses can have focal lengths which are all within one class of lens, such as the Sigma 10-20mm f/4-5.6 EX DC HSM Lens, which stays solely within the wide angle range of focal lengths. Zoom lenses can also have focal lengths which span lens classes such as the Nikon 18-200mm f/3.5-5.6 G ED-IF AF-S VR DX Lens which runs the gamut from wide angle, through normal, to telephoto focal lengths.
Let’s look at why photographers prefer prime lenses.
- Quality – While the quality of zoom lens optics has dramatically improved during recent years, and will continue to improve as new optics designs for zoom lenses are implemented, to date, it is generally true that prime lenses within each class of lens (professional or amateur) have better quality optics. To focus within a range of focal lengths, the optics of zoom lenses are far more complex than prime lenses, and therefore more difficult to design into the lenses, the same exceptionally sharp image quality which most prime lenses can produce.
- Low Light Speed – Generally prime lenses are faster than zoom lenses. That is, their maximum aperture is larger than the comparable maximum zoom lens aperture. For example, the AF VR Zoom-NIKKOR 80-400mm f/4.5-5.6D ED has a maximum aperture of 5.6 at 400mm, while the AF-S NIKKOR 400mm f/2.8G ED VR prime lens has a maximum aperture of 2.8, two full f/stops larger. That can be a significant help for wildlife photography, for example, when you’re out in a dark overcast day, or near sunset. Zoom lens improvements are beginning to lessen the advantage, but generally the advantage still exists.
- Weight – Often, prime lenses are smaller and lighter than zoom lenses which have a maximum focal length equal to the prime lens focal length, but there are exceptions to this. You need to compare lenses on a lens by lens basis.
- Flexibility – Zoom lenses allow photographers to quickly change focal lengths within the specific focal length range of the lens, which allows the photographer to reframe the subject without having to change lenses. Therefore the photographer can quickly change the photograph’s perspective and vary the images within seconds. During wildlife shoots, this can be especially helpful. Often one will see a bird singing in a nearby tree, then another at distance. Birds don’t normally stay in one place for long. In the time it takes to swap lenses you could miss a great shot. You could have each lens on separate bodies, but when hiking, that can be very heavy.
- Weight and Portability – For the travel photographer, this can be a big deal. While I know my Nikon 18-200mm f/3.5-5.6 G ED-IF AF-S VR DX has some optical weaknesses, it is capable of being used for wide angle, through normal, to telephoto photographs without swapping lenses. The lens weighs just 1lb 4oz. If I would replace it with a 16mm, 50mm, 105mm and 200mm lens the total weight of the lenses would be about 9lbs, plus I’d have the bulk of 4 lenses to pack in my camera bag. Clearly, there is a trade-off between quality and flexibility, but with zoom lens quality improving year after year, choosing a zoom lens to replace prime lenses is becoming easier.
From the above discussion, you can see that there are a whole range of considerations to ponder to determine which lenses will work best for you. There are other factors too, of course, your budget being of major concern. Moreover, even your travel location is an important consideration, and the types of locations you’re visiting while traveling.
Personally, I use a combination of prime and zoom lenses.