As Leica proudly proclaims, the 21mm f/1.4 Summilux is indeed the fastest 21mm lens ever produced. Let's take a closer look.
The Leica 21mm f/1.4 Summilux’s innovative 10-element, 8-group design incorporates two aspheric elements to achieve optimum image quality and color correction across the field, and one floating optical group to enhance its close-up performance. Considering its ultra-wide 90-degree coverage and super-speed f/1.4 aperture, its reasonably compact at 2.6 inches in length with a maximum diameter of 2.7 inches, but it’s on the hefty side (1.3 pounds) due to its solid all-metal construction and brass focusing helical.
Ultra-wide wonder: 21mm f/1.4 Summilux-M is the world’s fastest 21mm and its overall performance is spectacular on the full-frame digital Leica M9. Auxiliary finder is OK but not up to the same standard.
Image quality: Praise!
Generally, 21mm lenses covering the 35mm format have some linear distortion (typically, barrel type) and many exhibit noticeable light falloff (vignetting) at the edges and corners of the field. I found the performance of this lens to be exemplary in both respects. Linear distortion was negligible for a lens of this type, and light falloff (an unavoidable optical characteristic of all wide-angle lenses that increases with the coverage angle) is hardly objectionable even when examining images of uniform-toned subjects shot at f/1.4 and f/2.
This observation applies to pictures shot with the digital Leica M9 (which uses software to enhance evenness of illumination based on identifying the lens in use via the 6-bit code engraved on the lens mount) and of 35mmm images shot on Kodak Ektar 100 film with the Leica M7.
The outstanding sharpness and brilliance of this 21mm f/1.4 is evident even in pictures shot wide open at f/1.4. The combined visual effect of ultra-wide-angle coverage, superb definition at the point of focus, plus relatively limited depth of field (for a 21mm) is truly breathtaking.
Obviously, the depth of field zone increases markedly as you stop down. At apertures of f/5.6 to f/16 the zone of sharpness is so great that you can scale focus the lens, or set the hyperfocal distance according to the legible depth-of-field scale and use fixed focus.
Imaging performance at all apertures is excellent across the field. Amazingly, there is no discernible penalty to pay for its super-speed maximum aperture. The 21mm focuses with silky smoothness, and the finish is flawless.
Dynamic diagonals: Oblique ultra-wide composition plus shallow depth of field delivered by the 21mm Summilux-M shot wide open at f/1.4 allowed me to capture this unique perspective.
The only complaints I can come up with concern the lens shade, which is understandably large and adds to the bulk of the lens, and the accessory shoe-mount viewfinder. The Leica 21-24-28mm finder I used has some distortion, but more important, it lacks parallax compensation, and eyeglass wearers cannot get their eyes close enough to the eyepiece to see the entire finder field. The 21mm focuses down to 0.7 meters (2.3 feet), so parallax at close distances makes precise framing a challenge.
Despite these nits, this is truly a magnificent piece of glass. It can capture images of splendid quality at all apertures and shooting distances across its vast ultra-wide field. It’s very well corrected for flare. For those who require its sterling virtues and can afford its wallet-bending price, I can highly recommend this lens.