Digital Lenses: The f stops here

Lenses: family feud

As a whole, the new digital lenses outperformed their older 35mm film lenses at ultrawide and wide-angle focal lengths-but the differences in resolution and light falloff were less noticeable at higher apertures such as f/8, f/11, and f/16. Tip: If you have an older lens and want to maintain resolution and reduce light falloff, stop down to f/8 or smaller. But get a tripod if your shutter speed gets too slow to handhold the camera. Boosting the camera's ISO sensitivity to get faster shutter speeds magnifies resolution and contrast differences between the center of the image and edges.

Sigma's new digital lens outperforms its moderately priced 35mm sibling in terms of contrast at all aperture settings-proving the advantage of anti-reflective lens coatings. But several of the more expensive ultrawide-angle zoom lenses, such as the 16-35mm f/2.8L USM EF Canon lens ($1,390 street), contain aspherical lens elements with anti-reflective coatings. That may be why this lens outperformed the only Canon digital lens, the 18-55mm EFS lens ($100) at comparable 18-, 28-, and 35mm settings.

Nikon's new 12-24mm f/4G ED DX-series Nikkor is a digital-only lens. At 24mm, it just edged out (pun intended) the lower-priced 24-85mm f/3.5-4.5G IF-ED Nikkor lens in terms of resolution and light falloff at the widest aperture settings (see chart). Results evened out at higher apertures, and there was little contrast difference between the two lenses at any aperture.

There's no equivalent Nikon lens to challenge the new DX series at the 12mm setting, so if you want an ultra-to-wide-angle-zoom field-of-view for the D100, D2h, or D1x, this lens is your best choice. However, don't expect miracles at the 12mm setting. Images shot at this focal length show a 50-percent resolution dropoff and noticeable light falloff around the edges at f/4. By f/16, however, corner resolution was within 10 percent of the center. (So if you're shooting in low light, bring that tripod.)

The bottom line? The "digital-only" lens category is relatively new and growing rapidly, but it's no marketing ploy. If you have good 35mm ultra- and wide-angle lenses, as well as normal-to-telephoto lenses, keep them. But if you're starting out, opt for digital-only or digitally optimized lenses for better edge-to-edge sharpness, contrast, and brightness.

Download our Digital vs Conventional Lenses Chart

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