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They promise wider and longer shooting at a lunch-pail price. But are they any good?

AN ADD-ON ARSENAL: (Below) Nikon Coolpix 5700 with, from left: adapter ring, 0.8X wide-angle converter, 1.5X teleconverter, and fisheye converter. They’re big and fairly pricey ($130-$200), but deliver high image quality.

So your slick new 5-megapixel point-and-shoot has a great zoom lens, but it doesn’t go wide enough to get that great everybody-around-the-table shot? Or you wish it were longer at the tele end so you can bring in those distant mountains without losing picture quality by going to digital zoom? One good way around these optical limitations is a wide-angle- or telephoto-conversion lens, a moderately priced( $39-$130) optical device that mounts in front of your digital camera’s zoom lens and widens or narrows its angle of view. Just mount the converter and frame your shot on the LCD screen-what you see is what you get. It sounds almost too good to be true. Is it?

Back in the heyday of twin-lens-reflexes and rangefinder 35s, wide-angle- and telephoto-converter lenses were considered cheap and nasty alternatives to interchangeable lenses (though Rollei, for example, produced very fine-and expensive-ones called Mutars). While a digital SLR is undoubtedly the best solution for anyone wanting the ultimate in optical flexibility, today’s digital converter lenses work much better than you might expect, partly because they perform better with the shorter-focal-length lenses used on most digital formats. They’ve got a few operational snags, but they’re generally very easy and satisfying to use and have a high bang-for-the-buck factor.

Digital converter lenses come in three basic flavors: 1) screw-mount units that use a threaded ring on or around your camera’s lens; 2) bracket-mount units that fit onto or into a tripod-socket-mounted adapter bracket; 3) magnetic-mount units held in place by a thin, powerful, ring-shaped magnet that attaches permanently to your camera’s front lens ring. Each of these systems is workable, and each has advantages and disadvantages. Optically, the screw-in system provides the most precise converter-to-lens alignment. That’s one reason the major camera companies like Canon, Minolta, Nikon, and Olympus, as well as several independent makers, offer screw-mount converters and adapters. The bracket- and magnetic-mount systems offer greater mounting flexibility and are really the only way to attach converter lenses to the legions of compact digital cameras lacking threaded accessory-mounting rings.

How good are the images?
In general, lens converters for digital cameras perform surprisingly well when used with digital cameras in the 3- to 5-megapixel range. Most deliver good enough image quality for 4×6, 5×7, or even 8×10 prints. When shooting at maximum aperture, however, there may be slight softness at the edges and corners of the frame, and most wide-angle converters do exhibit some barrel distortion. Some converter lenses, like the Nikon optics (left), are big, and may block the camera’s viewfinder and pop-up flash. As a class, screw-in converters by camera manufacturers for their models perform better than generic converters made by independent manufacturers-hardly surprising, since they are matched to specific lenses. But, these differences are smaller than I expected and I found only one sub-par performance: a magnetic-mount wide-angle converter (sold under the Bauer, Phoenix, and Sunpak labels) on a Canon PowerShot SD100. Other defects, such as color fringing, were not objectionable until the prints were enlarged to 11×14 or greater. Conclusion: Converter lenses for digital cameras are worthwhile and cost-effective in extending optical versatility, and they perform well enough for all but the most critical shooting applications.

Operational pluses and minuses:
Screw-mount converters:
Plus: Secure, precise mounting, less light falloff, close focusing not impaired.
Minus: Relatively large, some heavy enough to affect camera balance, may require adapter rings.
Bracket-mount converters:
Plus: Secure mounting, little light falloff or focusing restrictions.
Minus: Camera bulkier due to bracket, mounting takes extra time.
Magnetic-mount converters:
Plus: Quick, easy mounting, converters very light and small, may mount on more than one camera.
Minus: Permanently mounted magnetic rings must be precisely positioned, are hard to remove, some noticeable falloff in corners/ edges with certain camera/converter combinations.

CLOSE-UP CAVEAT: Shot at left, zoomed to the max with no converter, is tack sharp. Right-hand shot with teleconverter added gets you closer, but focus is a tad soft. Moral: Don’t use teleconverters at or near minimum focus distance – back off a bit.

TELE TERRIFIC: At normal distances (25 feet) maximum zoom, no converter shot (left) and same shot with 1.5X converter added (right) both show excellent detail. Wide-angle converters add barrel distortion, may show a touch of color fringing in big blowups.