Zoom versus prime lenses

Overall, lenses are divided into two main groups: prime and zoom (see figure 6-2). A prime lens (also called a fixed lens) is one that has a fixed focal length, meaning the specification is a single length, such as 15mm or 200mm. A zoom lens has an adjustable focal length, meaning its focal length is a span, such as 24-70mm or 120-300mm. Both zoom and prime lenses can be in virtually any focal length — wide, normal, or telephoto. The following sections look at each type in more detail.

Zoom versus prime: Note the difference in how these two lenses are classified. The 50mm prime only has one focal length while the 70-200mm zoom lens has a range.

PRIME LENSES

Many discerning photographers believe that prime lenses have better quality and produce sharper, crisper images than zoom lenses. This is because there are fewer moving parts and optical elements involved in the lens mechanics. Fewer glass elements means less light and detail are filtered by any optics, and a less complex mechanical infrastructure means more precision.

Prime lenses are generally preferable if you can deal with the inconvenience of not being able to change focal lengths. For example, Canon’s 50mm lenses, which provide a very real-world, 1:1 magnification, are workhorses in portrait studios, and many professional photographers choose to move themselves in and out instead of giving up the quality they perceive the lens offers.

I suggest that if you are producing museum-quality images where using a prime lens is realistic (in other words, where you don’t have to change focal lengths quickly), then by all means use one. You’ll undoubtedly be pleased with the images you produce. And, even if you do need a zoom in your work, you might want to have at least one fixed-length lens, such as a 50mm, as an option for specific situations where its simplicity and quality will be welcome.

ZOOM LENSES

Zoom lenses are very convenient, especially in situations where you don’t have the luxury of moving around, or you can’t get to a spot fast enough or that is close enough to shoot. A tremendous amount of optical engineering has gone into developing zoom lenses that produce very accurate, high-quality images that can compare favorably with prime lenses of similar focal lengths.

Even in the studio, a number of excellent portrait photographers opt for a zoom lens and being able to conveniently change their focal length on-the-fly — and they still feel that the quality is more than acceptable. With convenience comes a price, however; while not 100-percent comparable, zoom lenses of similar speed and quality are typically more expensive than prime lenses — but you’re getting the equivalent of multiple prime lenses with a zoom (at least from the standpoint of focal length).


NOTE

Sometimes a telephoto lens is mistaken for a zoom lens; while many telephoto lenses are also zoom lenses, these terms are different. A telephoto lens is a lens meant to magnify distance, while a zoom lens is a lens that lets you adjust focal length to suit your composition.

Category: Science of Lenses

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