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Tuesday, December 1, 2009

Choose Your Perfect Zoom

The modern zoom lens is a marvel of technology, and it’s the nature photographer’s best friend

This Article Features Photo Zoom

Sigma 17-170mm
ƒ/2.8-4.5 DC HSM

Lens Speed
Manufacturers often offer a zoom range in two versions: faster and slower. For example, Canon offers 70-200mm zooms in ƒ/2.8 and ƒ/4 flavors. The former admits more light, so is better for dim-light shooting, as it allows for a faster shutter speed, offers a brighter viewfinder image and provides quicker autofocusing—and costs a lot more. The ƒ/4 is more compact and lighter, costs less and still performs very well—a great choice when you want to travel light or have a limited budget. Since many AF SLRs can’t autofocus with lenses slower than ƒ/5.6, the ƒ/2.8 lens offers another advantage: You can attach a 2x teleconverter, and the resulting 140-400mm ƒ/5.6 combo will still autofocus (albeit somewhat more slowly than the lens alone). With the 70-200mm ƒ/4 and a 2x converter, you’ll be focusing the resulting dim ƒ/8 image manually.

Pentax DA* 60-250mm
ƒ/4 SDM

Variable-Aperture Zooms
Fixed-aperture zooms maintain their maximum aperture throughout their zoom range: A 70-200mm ƒ/2.8 has a maximum aperture of ƒ/2.8 at all focal lengths. Many zooms have variable maximum apertures: Sigma’s 150-500mm ƒ/5-6.3, for example, has a maximum aperture of ƒ/5 at 150mm and a maximum aperture of ƒ/6.3 at 500mm. Through-the-lens metering in digital and 35mm SLRs automatically compensates for this, but you’ll have to keep it in mind if using a handheld meter.

Tokina 11-16mm
ƒ/2.8 AT-X PRO

Tamron SP
F/5-6.3 Di
Twin-Ring Vs. Push-Pull
Most zoom lenses today provide two rings, one for focusing and one for zooming. Some use a single ring; rotating it focuses, and pushing it away from the camera body or pulling it toward the camera body does the zooming. Some photographers (myself included) prefer the two-ring design; others prefer push-pull. Before buying a zoom lens, try it out and see how you like its zoom control.

Nikkor AF-S 14-24mm ƒ/2.8G ED
Camera Format
You have to consider your camera’s format (sensor size) when choosing a lens for a specific task. A focal length that provides a moderately wide angle of view when used on a 35mm or full-frame digital SLR becomes a “normal” lens when used on an APS-C digital SLR because the latter’s smaller sensor “sees” less of the image the lens produces.

Sony 70-400mm ƒ/4.5-5.6 G
All the major lens manufacturers now offer lenses specifically designed for the smaller APS-C and Four Thirds System image sensors. Advantages include more compact lenses, since they don’t have to produce as large an image circle, and more effective delivery of the light to the smaller sensor for better image quality. Canon’s are called EF-S and can’t be mounted on larger-sensor (or film) EOS SLRs. Nikon’s are designated DX; if you attach one to a full-frame Nikon DSLR, the camera will automatically switch to a cropped DX format. All Olympus Zuiko Digital lenses were designed specifically for the Four Thirds System image sensors used in Olympus DSLRs. Pentax’s DA* and DA lenses were designed specifically for the APS-C sensors used in Pentax DSLRs and can’t be mounted on Pentax 35mm SLRs. Sony’s DT lenses were designed specifically for the APS-C sensors used in all Sony DSLRs except the full-frame DSLR-A900 and A850, and the full-frame cameras will crop to APS-C format when one is attached. Sigma’s DC lenses, Tamron’s Di II lenses and Tokina’s DX lenses were designed specifically for DSLRs with APS-C sensors.

Wide-Angle Zooms
Wide-angle zooms are those that start at a wide-angle focal length for the camera format. Popular wide-angle zooms among APS-C-format landscape shooters include Canon’s EF-S 10-22mm ƒ/3.5-4.5 USM, Nikon’s AF-S DX Zoom-Nikkor 12-24mm ƒ/4G, Pentax’s DA 12-24mm ƒ/4.0, Sigma’s 10-20mm ƒ/3.5 EX DC HSM, Sony’s DT 11-18mm ƒ/4.5-5.6, Tamron’s SP AF10-24mm F/3.5-4.5 Di II and Tokina’s 11-16mm ƒ/2.8 AT-X PRO DX. For Four Thirds System users, the Olympus Zuiko Digital 7-14mm ƒ/4.0 provides the widest views.

Popular with the full-frame and 35mm set are Canon’s EF 16-35mm ƒ/2.8L II USM, Nikon’s AF-S Nikkor 14-24mm ƒ/2.8G, Sigma’s 12-24mm ƒ/4.5-5.6 EX DG HSM, Sony’s Zeiss 16-35mm ƒ/2.8 and Tamron’s SP AF17-35mm F/2.8-4 Di.


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