Primes vs. Zooms

In this case, zoom (70-300mm at 300mm, 1/800, ISO 400, f/13)
In this case, zoom (70-300mm at 300mm, 1/800, ISO 400, f/13)

If you decide to move beyond the kit lens that came with your camera, the inevitable question then becomes which lens to get. There’s an insane number of options out there, since your camera’s manufacturer is likely to have a substantial stable of lenses, and there are also aftermarket alternatives (of varying degrees of cost and quality) available to you. From time to time, I’ll be explaining some of these options, starting today with a question that’s as old as the zoom lens itself: are you better off with another zoom, or with a prime?

Let’s address primes first. A prime lens is a lens that has only one focal length. Most manufacturers make primes at several different focal lengths, from the very wide (like an 8mm fisheye) to a traditional wide-angle lens (a 24 or 35mm, for instance), “normal” lenses (40-50mm, so called because they approximate the average human field of vision), and telephoto lenses, which start around 85mm and can go to 500mm or more. On the positive side, the relative simplicity of their optics, coupled with the fact that they have fewer moving parts, makes these lenses cheaper, lighter, and sharper than their zoom counterparts. They’re also faster and brighter (the common maximum aperture is f/1.4 or f/1.8, though lenses with f/1.0 and even f/.95 have been manufactured). On the negative side, you can’t zoom with a prime. You want a shot that’s either tighter, or wider? Take two steps (or more) forward or back. Also, where a single zoom might cover 18-55mm, it can take two or more primes to cover the same range (20mm, 35mm, and 50mm, for instance), meaning more space taken up in your camera bag, and more weight to lug around.

What about zoom lenses? When they were first mass-marketed, in the late 1950’s, the initial enthusiasm for their versatility and convenience was tempered by the realization that there were significant tradeoffs in optical quality. It’s a perception that’s stuck with zooms to this day, even though a modern zoom provides much higher image quality than would have been possible fifty years ago. The biggest advantage of a zoom lens is convenience; one zoom, as mentioned above, can replace two or more primes, and some zooms – like the 18-200 and 28-300 variants that are currently available – can substitute for far more than that.** There’s also a cost factor involved once you start comparing the cost of one zoom versus its equivalent set of primes. And there are times when taking steps forward or back just isn’t practical or safe, so it’s better to have a zoom at your disposal. On the negative side, faster, brighter zooms typically max out at a 2.8 aperture (and the consumer zooms typically start at an f/3.5 or f/4 maximum aperture), won’t have the same lovely bokeh*** as a prime, and can be very large and heavy. Also, because of their optical formulae, they can tend to have a variety of distortion issues; where a prime will typically show some barrel distortion, a zoom can show barrel distortion, pincushion distortion, and complex distortion, all in the same lens, at varying focal lengths and apertures, which can give you conniptions if you’re trying to keep straight what parts of the range are doing what.

So, zoom or prime? The short answer, I think, would be that there’s room in your kit for both. Some photographers will shoot only with one or the other type of lens; a more rational approach is to find which generally works for you, but keep one or two of the other type in your kit as well. If you shoot mostly with primes, this might mean having a long (say, 70-200 or 70-300) lens in your arsenal. If you are shooting with zooms (and especially if you’ve only ever shot with zoom lenses), having even one fast prime in your kit opens up opportunities you didn’t even realize you were missing.

Obviously, regardless of which category you fall into, there are tradeoffs you need to be aware of. These will impact not only your wallet, but also your photography; it’s helpful, therefore, to do your homework, not only by researching the wealth of reviews and information that’s available on nearly every lens, but also by getting to a camera shop and trying the lens(es) on your camera.

*Before someone takes me to task for my terminology: a telephoto, strictly speaking, is a lens whose length is shorter than its focal length. So a 500mm lens wouldn’t necessarily be a telephoto if it were 500mm long, it would be a “long focus” lens. It would also be quite the pain in the neck to carry. At any rate, since “telephoto” is the going parlance for pretty much anything over 85mm, that’s the sense in which I’m using it here.

**Albeit with significantly compromised quality. An 18-200 has become the only lens for some shooters, and a convenient walkabout lens for many others who don’t always want to schlep their whole kit. Problem is, image quality at the ends – the widest and longest parts of the lens – tends to be a bit on the mushy side, especially in the corners (among other issues). You may decide that’s an acceptable tradeoff, but here again, it’s important that you try before you buy.

***Bokeh is a term referring to the little rounded bits of light that are out of focus in your photos. Some photographers, especially if they specialize in portraiture, pay closer attention to the bokeh than they do to the sharpness of a lens. It’s a purely individual decision and creative choice.

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