David Pogue's Digital Photography: The Missing Manual

Film Equivalents

Whenever people write about SLR lenses—on the Web, in reviews, in magazines—they always give you this weird little parenthetical: "The Nikon D60 comes with an 18 to 55 mm lens (27 to 82.5 film equivalent)."

You might have wondered what the deal is with that. And you wouldn't be alone.

Truth is, the number of people who care about the film-camera equivalent, or even understand what it means, is rapidly dwindling. Sorry to depress the old-timers, but film is just about dead.

The intention, of course, is good. If you're used to using a film camera, and you know how big the scene looks through a 50 mm lens, then you might be startled to find out that on a digital SLR, a 50 mm lens gives you a much smaller field of vision.

This all comes about because a digital camera's light sensor is not the same size as a frame of film (except on the most expensive digital SLRs—called full-frame SLRs—which require no multiplier).

Tip

For lots of good detail on the multiplier problem, visit www.lonestardigital.com and click the article "Multiplier Effect."

To make matters worse, there's no standard multiplier. A 24 mm lens on a Nikon digital camera does not give you the same wide angle as a 24 mm Canon lens. (You'd multiply the Nikon by 1.5 to get the film equivalent, the Canon by 1.6.) Then came the Panasonic/Olympus SLR format called Four Thirds, which has a 2X multiplier (a 40 mm lens is the equivalent of an 80 mm film lens). Some Kodak models have yet another multiplier.

The world ...