I frequently receive emails from beginning photographers who have heard that prime lenses are better than zoom lenses, and they want to know if they should buy a prime. A prime lens is simply a lens that cannot zoom from one focal length to another; in fact, prime lenses are often referred to as fixed focal length lenses. A “yes” or “no” answer to the debate surrounding the prime vs. zoom lenses question is far too simplistic, so I thought it would be helpful to explain the issues that should be considered before choosing prime or zoom lenses for your DSLR camera.
Why did photographers stay away from zoom lenses in the past?
Lenses are incredibly sophistacted tools that require precision engineering and ingenuity to achieve crisp images, fast focus, and low costs. Try to imagine an engineer designing a lens 15 or 20 years ago. They literally used slide rules and primitive four-function calculators. Such an approach would be impossible in today's world. Further, the lenses were often created for cheap film cameras that simply did not produce the detail of today's DSLRs.
When a zoom lens is created, the engineers must design the lens to produce sharp images at any focal length within the lens's range. Not surprisingly, this task was not precise without the aid of computers. Further, the lenses themselves did not have computer chips in them to transfer critical information to the camera and within the lens.
The long and short of it is that zoom lenses used to be a disaster. The images were rarely sharp. Lens engineers did not have the tools available to them to create advanced zoom lenses.
Do prime lenses have advantages over zoom lenses even today?
In short, yes! For the very reasons stated above, prime lenses can be produced much more cheaply and with greater sharpness than zoom lenses. Also, because the focus ring does not need to search as far a distance to find focus since only one focal length is available on prime lenses, prime lenses always focus faster than their zoom lens counterparts if all else is equal.
Are prime lenses sharper than zooms?
In my experience, the answer is yes; however, not by the margin that many photographers make it out to be. Prime lenses are generally much sharper than cheap zoom lenses (under $500), but many of the pro level zoom lenses are on the same level as the prime lenses.
Also, keep in mind that even a prime lens will not produce sharp images if it is made cheaply. I often hear photographers comment on how sharp the Nikon 50mm f/1.8 lens is, but I have personally never found that lens to be anything more than acceptably sharp. Many photographers hear that “prime lenses are sharper” and somehow expect that to mean that ALL prime lenses are sharp, and that simply isn't true.
When to choose prime, and when to choose zoom
When it comes down to which lens to buy, the fact is that it depends greatly on the lens. For example, I would ALWAYS recommend that a beginning photographer purchase a 50mm f/1.8 lens (check the price here for Nikon, or here for Canon), but in my opinion that lens cannot approach the optical quality of the Nikon or Canon 24-70mm lens; however, the 24-70 is significantly more expensive.
If a photographer is interested in a super-telephoto lens for sports or wildlife photography, almost any professional photographer would prefer a prime super-telephoto to a zoom super-telephoto for the advantage of faster focusing, slightly sharper images, and the ability to achieve lower apertures.
When it comes to the prime vs. zoom lens debate, the real answer is that it depends on the lens. The purpose of this article is to bring to your attention the advantages and disadvantages of zooms and prime lenses, and to point out that the simplistic “primes are better” mentality is simply outdated and overly simplistic.