Leica Super-Elmar-M 1:3.4/21mm ASPH.

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The "2011" Leica M scuderia comprises 21 lenses with focal lengths from 16 mm to 135mm, divided in the classical three groups of wide-angle, standard and tele-lens. The wide-angle group consists of eleven lenses; there are four standard lenses and six tele lenses. More than 50% of all lenses fall in the wide-angle category; the combination of the accurate rangefinder mechanism and compact wide-angle lenses might underscore the premium position of the Leica M system for documentary and human-interest photography. Manual focus with the coupled rangefinder camera and short focal length lenses is demonstrably more accurate than the autofocus mechanism of current cameras, irrespective of type of camera.

The actual Leica strategy for M-lenses emphasizes two approaches: very high speed lenses with excellent performance and compact lenses of moderate speed with superb quality. The aperture gap between these two ranges is between two and a half and almost three stops: f/1.4 versus f/3.4 and f/3.8. A small difference in aperture size can be justified when lens volume is important (the Summarit lenses versus the Summicron lenses). Leica lens design is now so advanced that the difference in performance between an f/2 lens and an f/2.8 lens (wide open and stopped down) is difficult to detect.

The SEM 21mm has the classical specifications of Super-Angulon fame and might strike a nostalgic chord in seasoned Leica users. This new lens is commendably compact and of impeccable mechanical quality. Classical lenses could impress with a very solid feel, but sometimes lacked substance. The SEM 21mm offers the best performance of all Leica lenses of this focal length and is a significant improvement over the Elmarit-M 21mm f/2.8 ASPH that it replaces. The SEM 21mm is one of the very few wide-angle designs where the differences in quality between centre, edge and corner are superfluous. This well-balanced character is one of the hallmarks of the design. The optical prescription guarantees extremely high image quality at all apertures, over the full distance range from 70 cm to infinity and from centre to corner.

Modern Leica lenses are often used on sensor-equipped M-cameras with software to correct some characteristics of the lens. The SEM 21mm shows darker corners when used on film-loading M-cameras, but the inherent vignetting of more than two stops is effectively compensated by the software. Close inspection shows some darkening, but this of no significance. In olden days one used to classify lenses as cool or warm, but again this is now obsolete, as the automatic white balance will correct the colour bias to neutral.

The same approach holds for distortion, once an important characteristic of wide-angle lenses and now easily corrected with in-camera software and post-processing SEM21applications. Leica users who want this lens on their film-loading M-camera can be reassured: the SEM 21mm exhibits minimal distortion that is only just visible at the edges. Previous wide-angle designs offered poor performance in the outer zonal parts of the capture area by the combination of vignetting, distortion and a drop in definition and contrast. The new SEM 21mm has outstandingly good definition and contrast till the maximum image height of 21.6 mm; this performance is already available at full aperture of f/3.4.

It is illustrative to compare the performance of the SEM 21mm with the current SX 21mm: at f/2.8 the SX shows some curvature of field and astigmatism that is visible in the very fine structures and a visible drop in image quality in the outer zonal areas. At f/5.6 the SX 21mm almost equals the quality of the SEM 21mm, at least in the definition of the subject outlines and fine detail representation (5 -10 lp/mm), whereas the very fine textural details become softer. These two designs show the different balancing act between a high-speed lens and a compact lens with moderate aperture.

Performance
Wide open the lens delivers a very high contrast image of extremely fine details from centre to corner and edge. The recording capabilities are well above the Nyquist limit of the M8 and M9 sensors; to exploit the full resolution capabilities of the lens one needs the best available high-definition film emulsions and an impeccable disciplined technique. When stopping down one can discern some improvement in definition and contrast, but this is immaterial in most instances. Images taken at close quarters (from 70 cm to 1.5 meters) have the same characteristics with the inevitable slight drop in contrast: a choice of f/5.6 for best performance and increased depth of field is a good idea.
Control of veiling flare and reduction of secondary reflections is superb, bringing very crisp definition and clear reproduction of outlines and details. This behaviour is also responsible for the famous three-dimensional look of the Leica pictures. Contre-jour (backlight) conditions are mastered with superior ease and one searches in vain for colour fringes at the edges of steep bright-dark gradients (micro contrast). When the image is checked at the unrealistically high magnification of 400% on the screen (Capture One Pro) there is no trace of colour fringing. This is pure optical quality, not (yet) adjusted by in-camera lens profiles.
The out-of-focus (blur) characteristic gives very pleasant bokeh effects. Specular highlights are tightly contained in a small circular brightness spot and general blur lines are smoothly rendered without harsh delineations.
Technically the SEM 21mm is a close relative to the SEM 18mm: the behind-the-aperture-group is almost identical and includes the lens element with two aspherical surfaces. The difference of three millimeters in focal length is important for the design parameters: the SEM 21mm has just a little more optical finesse.
Conclusion.
The Super-Elmar-M 21mm f/3.4 ASPH. approaches the ideal lens design: one does not often encounter a high-performance optical cell with homogeneous image quality at all apertures, distance settings and image height from centre to 21.6 mm wrapped up in a compact high-quality precision mount, even in the Leica stable. The lens has an impeccable finish and operates with the Leica-typical combination of silky smoothness and solid
Diagrams
The data-sheet can be downloaded from the Leica site
Images.Below you will find some pictures to illustrate the performance of the lens. All pictures are developed in Capture One without any correction: the pure negative so to speak.

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