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Tuesday, April 24, 2012

Prime Time

Once mostly cast aside in favor of high-tech zoom lenses, primes, or single-focal-length lenses, are making a serious comeback with pro photographers

This Article Features Photo Zoom
Tokina AF100mm ƒ/2.8

Everything old is new again, and sometimes that goes for technology as well as style.
Since the 1980s, zoom lenses have come to dominate the SLR and later the DSLR markets because of their convenience and rapid improvement in design and construction. At one time, zooms had been shunned by professional photographers, but that stigma no longer exists. High-end modern zooms are, by and large, excellent pro-caliber tools. As the zoom lens whirlwind swirled, however, prime lenses were left by the wayside.

Tamron SP AF90mm F2.8 Di; Nikon AF-S Nikkor 35mm ƒ/1.4G; Nikon AF-S Nikkor 85mm ƒ/1.8G
HD video DSLRs have rekindled an awakening to the benefits of prime lenses, and suddenly, in 2012, we're seeing pros adopt at least one prime, if not several, to their stable of lenses. It's time to take a closer look at the benefits of prime lenses for still and video shooting because these forgotten stepchildren of the imaging world have a lot to offer.

Key Benefits of Prime Lenses
The three most important benefits that primes offer a professional photographer are speed, sharpness and creative depth-of-field control. Of these, creative depth-of-field control—the ability to have a very narrow depth of field and a beautiful, uncluttered bokeh—has been the main attraction of a new generation of professionals to prime lenses.

Speed. Among zoom lenses, photographers readily extol the virtues of a "fast" ƒ/2.8 maximum aperture lens. Zoom models with ƒ/2.8 or ƒ/4 are often in a manufacturer's high-end pro lineup. On the other hand, in many focal lengths, you can find inexpensive primes that are often ƒ/1.8 lenses, which have a two- to three-stop advantage.

At the high end, there are primes that are readily available with maximum apertures of ƒ/1.4 and even ƒ/1.2! For example, the Canon EF 16-35mm ƒ/2.8L II is a favorite go-to workhorse for many Canon pros. Canon also makes the EF 24mm ƒ/1.4L II which, at 24mm, has a three-stop advantage over the zoom. Compared to the popular Canon EF 17-40mm ƒ/4L, that 24mm ƒ/1.4 has a full four-stop advantage. That's huge. Nikon's lens lineup shows the same thing. The AF-S 17-35mm ƒ/2.8D IF-ED is the preferred wide-angle zoom for many Nikon professionals. On the prime side, the Nikon AF-S 24mm ƒ/1.4G ED has a three-stop advantage over the zoom.

Carl Zeiss Planar 85/T2; Sigma 85mm ƒ/1.4; Sigma 24mm ƒ/1.8
The speed advantages can't be overstated. Fast lenses are versatile, and when you combine three extra stops in the lens with the ISO performance in modern professional DSLRs, you can see how the advantages compound quickly. Faster lenses also play a role in the next aspect of primes we'll look at: sharpness.

Sharpness. Thanks to relatively simple designs and fewer elements than zooms, prime lenses are easier to correct for image-degrading optical aberrations. Therefore, they can have a potential advantage in sharpness and other image-quality characteristics over zooms. That's not to say that every prime lens is sharper than every zoom lens at a given focal length, but all things being equal, a prime lens often has a distinct advantage over a zoom. Lens tests with ISO 12233 charts and MTF data bear this out. Keep in mind that charts and graphs aren't necessarily the best way to evaluate a lens, but they're useful tools for making comparisons of one lens to another.


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