As professional digital cameras push past the resolution capacity of film, some photographers have begun to look at today’s lenses as a limiting factor. Things that weren’t picked up by silver-halide film can become striking artifacts on some digital cameras, and the significance of design issues becomes more apparent. Take for example, Canon’s superwide 16-35mm lens, which was recently upgraded so that its edge quality is enhanced; this change was largely prompted by the legion of digital shooters who were more critical of the softness in the edge thanks to enhanced resolution of the new sensors.
    On the other hand, computer-aided design has led to a new era in lens creation and coatings. Manufacturing processes and technologies such as image stabilization have resulted in a generation of low-cost lenses that in many ways leave older optics in the dust. For the photographic enthusiast or prosumer who once had to choose between professional level lenses or mediocre-quality beginner lenses, the field has changed. The marketplace is currently flooded with a wide array of lenses at varying price points, making choosing a lens all the more difficult.

Zooms vs. Primes

For the first-time shopper, it helps to know that lenses break down into two main categories: zooms and primes. Prime lenses have one focal length, while zoom lenses can be set to different zoom ranges with the turn of a dial. When zooms were initially invented, they were universally lower quality than their prime counterparts. But with recent improvements in design standards and techniques, it’s now more common to see professional photographers shooting with zooms than primes in the field, and the number of available zoom lenses has increased as more and more photographers embrace them.
    Still, there are some things that a zoom lens can’t do. You’re not going to find a zoom with the same wide f-stop across its range as you would find in a prime. For example, it’s possible to find many prime lenses in the f/1.2 to f/1.8 range, but it’s unlikely that aperture flexibility will come to zoom lenses anytime soon. That’s because the number of moving parts necessary to make a zoom lens function properly reduces the amount of light able to be transmitted through the lens. In order to keep price levels down, many zoom lenses have a variable aperture that stops down as the lens goes through its focal lengths.
    However, it’s not at all uncommon for a zoom lens to have an f-stop range of f/2.8-5.6, which simply means the lens will have a maximum aperture of f/2.8 at its widest setting and f/5.6 at its most telephoto setting, stepping between those two settings as the lens is adjusted. So if you’re looking for the most accurate, sharpest images possible, stick with a lens that’s got a fixed, wide f-stop across the whole range—a 35-70mm f/2.8, for example. However, if you want to get the most bang for your buck, or if you’re looking for a travel lens you won’t have to worry about handling with kid gloves, pick up a less expensive zoom with a variable f-stop.

Sensor Selection

Another issue to consider is the type of sensor used in the digital camera body that will be paired with the lens. Many digital cameras use sensors that are smaller than a full-frame of 35mm film—usually based instead on the APS film format—while the majority of lenses were designed around a full-frame system. Most consumer digital SLR cameras are based on the smaller sensors, so they have a focal-length multiplier—a number by which it’s necessary to multiply the lens focal length to find its conversion for the smaller sensor. For example, put a 70mm lens on a body with a 1.5 conversion, and it acts like a 105mm.
    Many companies have special lenses designed for these sub-full-frame sensor cameras; Nikon has a range of DX lenses designed specifically for these bodies, while all Olympus lenses are developed for their specific digital-only sensors. These types of purchase considerations can be crucial if you’re planning to upgrade camera bodies, as lenses designed for APS-sized sensors don’t work well on full-frame cameras. This ties into the purchase considerations for the new camera buyer as it means that a shopper should consider not only the purchase decisions of today, but also the upgrades of tomorrow. It’s easier to upgrade or change your camera body if you don’t have a huge investment to deal with.

Image Stabilization

One of the biggest advances in recent years has been in the area of image stabilization. By incorporating gyroscopes into either the lens or the camera body, companies have created optics that are less prone to the motion blur caused by hand-holding a lens. Some systems include image stabilization in the camera body, while other companies build this feature into the lens instead. Both systems work well, with lens-based systems easily replaceable (with new lenses) as the technology improves, and camera-based systems always available. In practical terms, image stabilization allows photographers to hand-hold a lens in several stops lower light than they would without the stabilization. This results in sharper pictures in a variety of situations where tripod-free photography would be impractical.
    It’s also a great advantage for companies who make lenses; it’s cheaper to add image stabilization to a lens than it is to create one with better light-gathering. Keep in mind that image stabilization won’t change the maximum aperture of the lens. While you may be able to hold your composition at 200mm in low light, you’re still faced with the limitations of the lens’s aperture. It isn’t possible to get the depth-of-field effect of a f/2.8 shot with an f/5.6 lens, regardless of the stabilization. With an image stabilized lens, you can shoot at f/5.6 where you might have had to up the ISO or shoot at f/2.8 on a nonstabilized system.

Specialty Lenses

Photographers not only rely on their standard lenses but also turn to specialty gear to get the right shot. For those looking to enhance their camera kits, macro lenses are the most common add-on. These lenses magnify the world, providing a unique, larger-than-life view of a subject. Hyper-macro lenses—like Canon’s 65mm 1x-5x lens, for example—take macro a step further with a nearly microscopic enhancement of the world.
    Perspective control, or “PC,” lenses are frequently used by architectural photographers to straighten the lines that converge or diverge when looking at an object with parallel lines. With a PC lens it’s possible to correct the distortion found in a standard lens, so if you’re shooting a tall building, the sides look parallel, as opposed to a distorted view where the walls look like they meet somewhere on the 100th floor.
    A favorite new lens for countless wedding and portrait photographers is the Lensbaby, a great little tool that was adapted from the large-format world to fit onto 35mm and medium-format cameras. Essentially a lens and a bellows, the Lensbaby can be bent and twisted to create all sorts of focus and perspective tricks. It’s great in creative art photography because you can selectively focus and defocus areas of the image in a way that’s not possible with standard lenses. Images that come from a Lensbaby look like they were created by Impressionist painters, not by photo-realists. Just as a painter picks the right brush for the stroke, keeping a good selection of practical lenses and specialty lenses on hand helps the photographer chose the right tool for the job.