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One of the best ways to see results in your photography is to be able to always work with the scene you are photographing, which is often accomplished these days through the usage of a zoom lens, as it isn’t always possible to move back and forth and still capture the subject you are photographing. However, the prime lens - a lens with a fixed focal length - still has its own uses: often, a prime lens has a fast maximum aperture, like f/1.8, a technical specification which has its own important uses.

When using a lens with a fast aperture, there are three things you’ll notice: better low-light performance, the possibility of more depth of field or blur, and how much sharper your images are at comparative apertures in similarly priced zoom lenses. As a quick definition, a fast lens doesn’t refer to the autofocus speed, rather the speed of the aperture. A “faster” aperture is one that lets more light in, allowing a faster shutter speed or a lower ISO.

1) Better low light performance.

Most zoom lenses these days have variable maximum apertures. This means that as you zoom in, the size of the aperture changes and less light is let through the lens, even if you’re already set to the maximum sized aperture (lowest f number). The designation of this usually follows the lens’s focal length on the box. For example, Nikon’s very popular super zoom, the 18-200mm f/3.5-5.6, has an maximum aperture of f/3.5 at the wide end, but as you zoom in, it is reduced down to f/5.6. While this can be compensated for with a slower shutter speed or a higher ISO, the low light performance of the lens is best at 18mm and worst at 200mm.

Now, let’s take a fast prime lens in to consideration. For example, the Nikon 50mm f/1.4D. Despite having no zoom function, this lens lets use use a maximum aperture of f/1.4, which is much brighter than the 18-200mm’s f/3.5. Not only this, but since the 18-200mm gets darker as you zoom, at 50mm the 18-200mm has a maximum aperture of only f/4.8.

With a fast prime lens, you can shoot at 50mm with a very fast aperture of f/1.4, rather than the slow aperture of f/4.8 using the 18-200mm. To put this in comparison, at f/1.4 and ISO400, if you required a shutter speed of 1/60 second, at f/4.8 and ISO400, you’d need a shutter speed of 1/8 of a second.

50mm f/1.4D - f/1.6, 1/3s, ISO800

2) Less depth of field

The wider aperture of the faster lens makes for less depth of field - the distances between which subjects appear sharp, which is useful in many situations. You can blur a distracting sign in the background when taking portraits, or you use it for creative effects. Using less depth of field is great for a more unique look that is really only available in digital SLRs or film cameras. When using a point and shoot or a camera phone, the image sensor is so small and the lenses are of a relatively high aperture that makes depth of field very hard to control in general photo taking - many portraits have the background in focus too. Notice in the image below how you are drawn to the subject’s eyes, rather than a distracting background.

Taken with a Sigma 20mm f/1.8 on a D300

3) Comparatively sharper images.

A prime lens’s advantage is often its simplicity. Light, inexpensive, fast. Also, since it does not need as many pieces of glass in the lens, it is less prone to flare or other issues that can lead to reduced sharpness. In the photo on the left, taken with a Nikon 50mm f/1.4D at f/5.6 on a Nikon D80, you can see that the lens is very sharp. On the photo on the right, taken with an 18-200mm f/3.5-5.6 at f/5.6, you can see that this lens doesn’t have the same resolving power as the lighter, cheaper, faster prime lens.

Both images at f/5.6, 1/60s, ISO160 on a Nikon D80

Recap and Suggestions

Having a light prime lens in your bag can make a world of difference when the sun goes down or you step inside, because of the faster aperture. However, the creative effects of this lens have usage even on a well-lit day or even in the studio. Even in the retail market, there are inexpensive prime lenses for all makes of camera. If you’re willing to look at the used market, there are thousands of these fast lenses because before the creation and optimization of the zoom lens, these were the standard lenses that came with the camera.

If you are a Nikon user, the 50mm f/1.8D is a good budget choice. If you have a bit more money and want a higher quality product, the 50mm f/1.4D is the way to go.

If you are a Canon user, the 50mm f/1.8 is a good lens at a less expensive price as the Nikon equivalent. However, you also have the option of more expensive 50mm f/1.4 USM, or the professional [and very expensive] 50mm f/1.2L

If you are a Pentax user, they have a 50mm f/1.4. If you prefer Sigma lenses, they too have a 50mm f/1.4 lens. For Olympus users, you’ll need a Sigma 30mm f/1.4 lens, as Olympus doesn’t have any normal lenses faster than f/2 for the 4:3 mount. Of course, the Sigma is available in the other major mounts as well.

Of course, these links are all to retail, new-in-box lenses with a warranty. If you decide to go the used route, especially for camera makers like Canon or Nikon, there are manual focus lenses from older film cameras like the Noct-Nikkor 50mm f/1.2, which had legendary sharpness even when used at its maximum aperture. Canon even made a short-lived lens for their Canon 7 rangefinder that had an aperture of f/0.95!

While the 50mm fast prime lenses are the most popular, they are not the only focal length available. There is the brilliant Sigma 20mm f/1.8, available in mounts for Canon, Nikon, Sony and Sigma, as well as expensive telephoto lenses like the Nikon 200mm f/2 or the Canon 135mm f/2L. The Nikon and Canon “portrait lens” solutions are generally a fast 85mm prime, such as the 85mm f/1.4D or f/1.8D in Nikon mounts or the Canon 85mm f/1.2L or f/1.8. There is also an expensive Zeiss manual focus 85mm f/1.4 lens of very high quality available in Nikon or Pentax mounts, with an auto focus model for Sony cameras.

Other features of fast prime lenses are things like “Tilt-Shift” features, available in a 24mm f/2.8, 45mm f/2.8 or 90mm f/2.8 manual focus Canon lens, or an 85mm f/2.8 manual focus Nikon lens.

While zoom lenses are the most common in photography today, there is a huge number of quality prime lenses at pretty much any price point, many of them offering things you cannot achieve in a zoom lens, like a fast f/1.4 aperture or Tilt-Shift capability.

If you have any favorite fast, prime lenses that you think we’ve left out, post them in the comments. If you’ve read this far, perhaps consider digging the story.

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