What looks like a zoom, is used like a zoom, but isn't a zoom? Leica's 16- 18-21mm f/4 Tri-Elmar-M ($3,495, street). With three individual focal lengths in a single housing, and no intermediate settings, this 21-24-28mm equivalent (on the M8 digital) doesn't zoom, but click-stops through its focal lengths.
With the substantial feel and all-metal construction for which Leica is known, the Tri-Elmar offers a nicely damped turning action for the focal length and aperture rings. Its closest focusing distances are in faint gray and can't be set. Their purpose? Indicating the closer distances that can be rendered in acceptably sharp focus due to depth of field. The gray distances line up with the lens' extensive depth-of-field scales.
The Tri-Elmar's lens shade is also unusual: It has a window cut through its body, so you can see through the shade when viewing with the M8's rangefinder. (Notice the red threading on the barrel in our photo? It's to remind you to use the shade!)
In The Lab:
No surprise here: SQF data showed Excellent contrast and sharpness at all three focal lengths. Distortion was also well controlled -- in the Visible range at 16mm (0.33% barrel), and Slight at 18mm and 21mm (0.24% and 0.13% barrel distortion, respectively). Light falloff left the corners at f/5.6 at all three focal lengths, a slightly above-average performance for the ultrawide class. As is usual with Leica lenses, closefocus left something to be desired, with maximum magnification ratios ranging from approximately 1:23 (16mm) to 1:19 (21mm) at the uniform close-focusing distance of about 19 inches.
For wellheeled Leica fanatics, and especially M8 digital owners, this ultrawide is appealing. Don't forget that it requires Leica's shoe-mount Universal Wide-Angle Viewfinder M for accurate framing. Cleverly designed to automatically correct for parallax (after you manually dial in the subject distance), this $740 (street) viewfinder is discounted to $400 when bought with the lens.