The new Super Elmar-M 21mm f/3.4 ASPH (about $2995) looks to fill a gap in the M line with another highly compact and very high performance wide angle, joining the 18mm f/3.8 Super-Elmar-M ASPH and the 24mm f/3.8 Elmar-M ASPH (both highly recommended).
The “tab” focusing as seen at right side of the lens does not offer the fine finger control as with a knurled focusing ring, at least not for me; tab focusing is found on many of the smaller M lenses. But the compact size apparently demands the tab approach.
Performance according to the MTF charts looks to be near optimal wide open at f/3.4 for coarse structures (very impressive), improving only very slightly by stopping down to f/5.6 for fine structures and for contrast in corners. This is a very high performer. The MTF charts also suggests a nearly flat field, and there is absolutely minimal astigmatism, both attributes that are admirable for digital (see Making Sharp Images).
Distortion (wave type from barrel to pincushion) looks to be very low for a 21mm lens, though not nearly as low as the Zeiss ZM 21mm f/4.5 Biogon (which unfortunately has color shading issues on the M9 due to extreme ray angles).
Nominal, as per Leica.
|Angle of view
(diagonal, horizontal, vertical):
|for 35mm (24x36mm): 91°, 80°, 59° for M8 (18x27mm): 74°, 64°, 46° (Equivalent focal length : approx. 28mm)|
|Optical design:||Number of lenses/groups: 8 / 7 Aspherical surface: 2
|Position of entrance pupil:||Position of entrance pupil: 15,6mm (related to the first lens surface in light direction)|
|Focusing range:||0.7m to infinity|
|Distance setting Scales:||Combined meter/feet graduation|
|Largest reproduction ratio:||1:29.4
706 mm x 1059 mm (35mm) / 530 mm x 795 mm (for M8)
|Aperture:||With click-stops and half-stop clicks, f/3.4 to f/16|
|Bayonet:||Leica M quick-change bayonet with 6 bit lens identification bar code for digital M models|
|Filter mount:||female thread for screw-on filters size E46
Male thread with stop for lens hood (included in delivery)
|Dimensions:||43/55mm (with/without Lens hood), diameter 53 mm|
Leica’s description of the 21mm f/3.4 Super-Elmar-M ASPH:
With the LEICA SUPER-ELMAR 21 mm f/3.4 ASPH., Leica is extending the range of M lenses in the super wide angle range with a model that combines outstanding reproduction with a compact design. It delivers uniformly excellent reproduction quality over the entire field of view, with only a very slight deterioration at the edges in the close-up range. This performance can only be improved slightly by stopping down, which means that you can take photo- graphs with full stop with no concerns, unless your compositional ideas call for a greater extension of the depth of field that can only be achieved with smaller apertures.
The vignetting characteristic of every optical system is more pronounced on a super wide-angle lens than on normal lenses and those with long focal lengths. At full stop in 35mm format it is a maximum, i.e. in the corners of the image, of around 2,1 stops, around 1,2 stops on Leica M8 models with their slightly smaller format. Stopping down to f/5.6 reduces this light falloff at the edge of the image – to 1.6 and 1.0 stops respectively. Stopping down further does not result in any further reduction as essentially only the natural vignetting remains. The maximum distortion of the lens of around 1.5 % is hardly perceptible.
The retrofocus-like construction is made up of a total of eight lens elements, and the use of a lens element with two aspherical surfaces and four lens elements made of glass types with anomalous color dispersion (partial dispersion) make a crucial contribution towards restricting aberrations to an absolute minimum.
Summary: The LEICA SUPER-ELMAR-M 21 mm f/3.4 ASPH. combines optimum reproduction with compact dimensions, offering all M users a wide range of options in the spontaneous super wide-angle photography that is typical of the Leica M.