Prime Lens 101

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By Joshua Kleiner

Published: Wednesday, November 20, 2013 - 11:07am

Whether shooting a DSLR or mirrorless camera, interchangeable-lens cameras significantly broaden the photographer’s range of creative possibilities. There’s a good chance that the kit lens included with your camera was a zoom lens that offers a zoom range suitable for most of your initial photographic pursuits. A fixed focal length camera lens, or "prime" lens, offers a great way to improve the quality of your images while helping to develop your eye as a photographer. Now that you’re looking to take your imaging capability to the next level, here’s a brief guide to finding a prime lens that’s right for you.

Prime versus Zoom

Compared to a prime lens, a zoom lens is a general purpose multi-tool that won’t cut it when it comes to tasks requiring surgical precision. Think of a zoom lens as a Swiss Army knife and a prime lens as a scalpel. Prime lenses are capable of image quality and durability well beyond variable focal length lenses. Element for element, a prime lens will outclass a comparable zoom lens every time. Fewer moving parts and a defined field of view allow manufacturers to craft an optical path that is optimized for a specific purpose. A prime lens is generally capable of wider maximum aperture and is less susceptible to optical aberrations like color fringing and soft focus at the edge of the image.
The high-resolution sensors in today’s DSLRs and mirrorless cameras enable photographers to pack an impressive amount of detail into each frame—even an entry-level camera can capture HD video. A quality prime lens can provide tack-sharp detail and lifelike tonal range in recorded images.

Choosing a Focal Length

Obviously, choosing a suitable prime lens is largely based on its intended use. Since fixed focal length lenses lack the versatility of their zoom-lens counterparts. A prime lens will serve you well for specific applications and focal length is critical. The maximum aperture, minimum focus distance, quality of glass and optical coatings are important to consider regardless of focal length.

Keep in mind that the angle of view captured by any lens will change when it's mounted on a non-full-frame camera, like a DSLR with an APS-C sensor. A 35mm lens mounted on such a camera, with a 1.5x crop factor, for example, will have an equivalent focal length of 52.5mm. A longer focal length lens captures a smaller field of view. So a super-telephoto lens mounted on a non-full frame DSLR can yield a prohibitively narrow perspective. However, cropped-sensor shooters can benefit from a faster, wide-aperture lens, that will image super-telephoto distance usually thought to only be available to full-frame shooters—Nikon’s AF-S Nikkor 600mm f/4 ED VR AF lens or Canon’s EF 600mm f/4 IS II USM become 900mm mega-photo lenses ready to get up close and personal with sports and wildlife action.

Standard Lenses

Standard lenses have an angle of view close to 45°, replicating the perspective seen by our eyes. Although the quality and design of the optics determine its angle of view, the standard primes usually have a focal length between 40mm and 65mm. A favorite among photojournalists is the 50mm lens. Henri Cartier-Bresson, one of the most prominent photojournalists of the Twentieth Century and an icon for amateur and professional street photographers, famously used a 50mm lens almost exclusively. A standard focal length lens acts as “an extension of (the) eye” according to Bresson, permitting photographers to trap life in a frame that resembles the way we experience the world.
Like all lenses discussed in these sections, standard length lenses are available for DSLR and mirrorless camera formats. Canon’s EF 50mm f/1.4 USM lens is a budget-friendly standard focal length DSLR option for your first prime; its wide maximum aperture can capture photos or video in low-light situations.

Telephoto Lenses

Telephoto lenses are essential for portraiture as well as event photography like weddings, concerts, and sporting events. Telephotos have a lens group within their optical path to create an extended focus point that is longer than the overall lens design. In effect, telephoto optics allow photographers to image a subject at great distances using a relatively compact lens. These lenses generally have focal lengths greater than 80mm, but can also include shorter focal length pancake lenses featuring a telephoto lens design. Technically, not all lenses with a focal length more than 80mm qualify as a telephoto lens, but these lenses can have unwieldy lengths and tend to use outdated optical designs.
Two important factors to keep in mind with telephoto lenses is their maximum aperture and image stabilization technology. As the focal length of the lens increases, the challenge of transmitting light through the lens system also increases. Since the lens system has a narrower field of view from which to gather light, the diameter of each lens element must be increased to maintain an acceptable level of image brightness, which is why telephoto primes with a maximum aperture of f/4 or greater have large front lens elements and a corresponding increase in overall lens weight.
Additional size and weight, coupled with the narrow field of view, make image stabilization an essential feature of telephotos, especially once you exceed a focal length of 200mm. Lens manufacturers are aware of this limitation, which is why they equip their telephoto lenses with technology that provides several f-stops of image stabilization, allowing photographers to use their telephotos with slower shutter speeds and lower ISO camera settings.

Wide-Angle Lenses

At the opposite end of the focal-length spectrum are wide-angle lenses. The focal length of this type of lens is generally less than 40mm, which works well for landscape and architectural photography. When attached to APS-C or other non-full frame cameras, a wide-angle lens can have the equivalent focal length of a standard lens—something to keep in mind before purchasing a 35mm lens, which becomes 52.5mm when attached to a non-full frame camera with a 1.5x crop factor. For the most part, wide-angle lenses are a sensible general-purpose option for family vacations, backyard gatherings, and photojournalism.

Specialty Lenses

Included in the wide-angle category are fisheye lenses, usually a focal length less than 20mm. This type of specialty lens, Rokinon’s 8mm f/3.5 HD Fisheye Lens, for example, offers a unique perspective by capturing a surreal 180-degree angle of view—great for conveying the overall feeling of a location as opposed to the limited field of view of most lenses.
Macro lenses are another type of specialty lens that can give a larger-than-life quality to your photos and an especially unique perspective to videos. Macro lenses are available in various focal lengths, from wide angle to telephoto. A macro lens is uniquely equipped for close-ups, thanks to its short minimum focus distance and specially designed focus mechanisms optimized for fine focus adjustments. The Makro-Planar T* 100mm f/2 Lens from Zeiss is a standout example of everything a telephoto macro lens should be; it features the premium optics Zeiss is known for, and it delivers precise focus control required for exacting focus placement.

If still life and product photography, or extreme close-ups of blooming flowers and other natural beauties are subjects of your photographic interest, then a macro prime lens is uniquely suited to help achieve the best image quality possible.