Top Lens Choices For Digital Cameras

D-SLRs
Physically smaller than the film they replace, the imagers in D-SLRs capture a narrower slice of your lenses’ fields of view. This effect, known as magnification factor, makes a digital image taken with any given lens appear as though a longer focal length was used when compared to 35mm (it’s exactly the same issue you run into when putting a roll-film back on a 4x5 view camera). Most current magnification factors run from about 1.3x to 1.7x.

With a 1.5x factor, your 28-80mm lens has an angle of view like that of a 42-120mm on 35mm. On the one hand, that’s a benefit—your telephoto lenses just got “longer,” but without the speed-loss penalty of a telecon-verter. An 80-200mm ƒ/2.8 acts like a 120-300mm ƒ/2.8!

Photographers who already own long lenses will see their reach increased. New buyers also can choose to get shorter lenses than they otherwise would have for the same equivalent focal length they’d use with film. (The 80-200mm lens for a 35mm film camera can be replaced with just a 50-135mm lens on a digital camera with a 1.5x factor.) That approach reduces the size and weight of the photographer’s gear and opens the possibility of faster lenses as well.

Magnification factor also affects your wide-angle lenses, unfortunately, and their angles of view are narrowed, too. Your wide 24mm lens now seems more like a 36mm; to replace its angle of view, you’d need a 16mm lens on a D-SLR. Similarly, D-SLR shooters need an ungainly, ultra-wide 14mm lens to stand in for a 21mm on film. A slew of new lenses designed for digital SLRs address this problem.

Some of these lenses boast focal lengths that will seem surprisingly short and that would represent extremely wide-angle lenses on 35mm film. Such lenses would be difficult or impossible to create if they had to cover 35mm’s larger area, but are achievable for the D-SLRs’ small sensors. In part, this ability comes from the relative ease of designing lenses that cover smaller formats.

The new designed-for-digital optics take care of another problem as well: Unlike film, the individual photosites on imaging sensors perform better when the light comes straight in on them (think of each pixel location as a tall bucket into which you’re trying to drop light, and you’ll see the problem). Lenses optimized for digital collimate their light more than those designed for film, and minimize the risk of light falloff and image degradation at the corners of your photos.

Many of the lenses featured here employ upgraded multi-coating to combat a source of flare particular to digital photography: the imaging sensor itself. Unlike film, which has a relatively matte surface (as well as anti-halation coatings on its base), digital imagers have a shiny top layer. Mirror-like reflections off the imager can strike the lens elements, where less-thoroughly coated lenses will bounce the reflections back to the imager as flare. Along with minimizing that flare, the improved coatings increase contrast, especially in darker areas of your images.

Each of the manufacturers listed below is working steadily to expand its digital lens series. The current roundup shows not so much a range of esoteric lenses as the possible beginnings of larger systems.

Although Nikon’s DX-series lenses use the classic F-mount, the optics are designed exclusively for the compa-ny’s DX-format imaging sensors, all of which share a 1.5x magnification factor. Because they don’t have to cover the entire 35mm frame, they can be physically smaller and offer shorter focal lengths than would otherwise be possible. The four DX lenses include a 10.5mm fish-eye and a 12-24mm optic that has a 35mm-equivalent range of 18-36mm. The lenses also work on Fujifilm’s S2 Pro and S3 Pro D-SLRs.

Olympus has designed its new digital-only E-1 system from the ground up, and all six lenses are optimized for digital capture. It also capitalizes on the E-1’s smaller imaging sensor, which provides a magnification factor of 2x. Because of this, the new telephotos, in particular, are smaller, lighter and faster than their 35mm equivalents. The E-1’s 150mm ƒ/2, for example, provides the same magnification as a bulky 300mm ƒ/2.8 would do for 35mm, but is a full stop faster and more than one-third lighter than the larger lens.

Like Nikon, Pentax uses its film cameras’ lens mount for its digital-only lenses. Currently, Pentax offers two lenses in the line: a 14mm ƒ/2.8 and a 16-45mm ƒ/4. The 14mm’s 90-degree angle of view is equivalent to a 21mm on a 35mm camera, and the zoom has a 35mm equivalent of 24-68mm.

Sigma’s new DC-series lenses fit a variety of digital SLRs, including its SD-9 and SD-10, as well as Nikon, Pentax and Olympus E-1 4/3rds cameras, and small-format Canon D-SLRs. The 18-125mm zoom has 35mm-equivalent focal lengths of 27-188mm at 1.5x, and the 55-200mm is equivalent to an 83-300mm.

Tamron’s Di series departs slightly by optimizing its optics for digital, while still covering the full 35mm frame. The lenses work with full-frame digital sensors, as well as Canon’s EOS-1D and EOS-1D Mark II sensors, which have a 1.3x magnification factor. Among the five lenses in the current lineup are a 17-35mm ƒ/2.8-4 with an equivalent range of 26-53mm at 1.5x, and a 90mm ƒ/2.8 macro (equivalent to a 135mm) that focuses down to 11.4 inches.

Canon’s EOS Digital Rebel has a lens mount that accepts a special EF-S 18-55mm ƒ/3.5-5.6 “Rebel-only” lens in addition to the Canon EF line for EOS cameras. The rear of this new 28-90mm-equivalent optic sits closer to the image sensor than on other Canon cameras, as an aid in designing short focal length lenses. Because of this, the lens can’t be mounted on other Canon cameras, but new digital SLRs and lenses with this mount will join the lineup in the future.

Advanced Compacts
Accessory lenses for advanced compact digital cameras extend the wide-angle, telephoto and close-up capabilities of your camera’s built-in optics. Unlike a D-SLR’s interchangeable lenses, these add-on lenses attach to the front of your camera’s existing lens, and use the camera’s existing optics and other systems.

Because they don’t need to supply an ƒ-stop mechanism, focusing system or onboard electronics, accessory lenses are smaller, lighter and less expensive than a D-SLR’s interchangeable bayonet-mount lenses. These lenses aren’t as quick to change as D-SLR lenses are, though. While some add-on lenses screw directly into the filter threads on the front of your camera’s lens, many require special connecting adapters that first must be screwed or bayoneted into your camera.

Most wide-angle accessory lenses are between about 0.7x and 0.8x. If your wide-angle is equivalent to a 28mm, for example, multiplying that length by an adapter lens’ 0.8x factor gives you an effective length of just over 22mm—a very wide lens. Using a similar lens on a built-in zoom equivalent to a 35mm gives you a 28mm for moderate wide-angle coverage. Nikon makes an additional lens for some cameras in its Coolpix line—it provides an ultra-wide “fisheye” with an angle of view beyond 180 degrees.

Telephoto accessory lenses work in a similar manner. They fit over your camera’s lens and multiply its focal length about 11⁄2 times on average. If your camera’s longest lens is an equivalent of 200mm, it will be more like 300mm with the add-on lens.

Unlike the teleconverters familiar to SLR users, these add-on telephoto lenses have no effect on the maximum aperture of the camera’s built-in lens. This allows photography at high shutter speeds for handheld work or to stop action, and helps gather dim light after sunset.

Along with the camera manufacturers, independent makers like Century Optics, Kenko, Phoenix and Tiffen make accessory lenses that fit a wide range of cameras, from still to video. Because these add-on lenses are designed to work on many cameras instead of a few specific models, their performance will vary, depending on the camera, and may or may not be up to your standards. The best approach is to test a particular add-on lens and see if it works for you.

Multi-element, accessory close-up lenses aren’t just for digital—they’ve been made for film cameras for ages. These highly corrected, filter-sized attachments fit on the front of your built-in lens like other adapter lenses, and can screw into the front of your D-SLR’s lenses, too. They work very much like achromatic “reading glasses” to correct your camera’s farsightedness, allowing the camera to focus closer than it could otherwise. Some multi-element close-up lenses that fit digital cameras, like those from Canon, Century Optics and Hoya, provide outstanding optical quality.

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