Leica 35mm f/2.5 Summarit-S ASPH
Related: distortion, Leica 35mm f/2 Summicron-M ASPH, Leica M, Leica medium format, Leica S 35mm f/2.5 Summarit-S ASPH, Leica S Typ 006, medium format, MTF and Micro Contrast, optics
The Leica 35mm f/2.5 Summarit-S ASPH is the (only) wide angle lens for the S2 as of July 2010, equivalent to a 28mm lens on a full-frame 36X24mm DSLR.
With medium format cameras, wide angle lenses are hard to come by, but with the S2’s 45mm X 30mm sensor, one can reasonably expect that a ~26mm lens might eventually emerge (eg 21mm equivalent).
Leica states that the 35/2.5 “operates practically without distortion”, which to me means less than 0.5% distortion, but to Leica might mean up to 2%. No distortion graph is provided.
It seems likely that Leica will bring a wider angle lens to the market than the 35mm, perhaps a ~26mm lens (21mm equivalent). I’d also hope to see a 45mm lens (equivalent to 35mm on a 35mm camera).
Nominal, per Leica.
Close-focus capability is adequate, but the 1:11 reproduction ratio does reduce the versatility for enjoyable close-range shooting.
|Specifications for Leica 70mm f/2.5 Summarit-S ASPH|
|Focal length||35mm (nominal), equivalent to 28mm in 35mm terms|
|Lens construction||11 elements in 9 groups with rear group focusing and 2 aspherical surfaces, five special glass elements with anomalous partial dispersion|
|Focusing range:||21.7" = 55cm|
|Smallest object field:||1:11 reproduction ratio|
|Item Angle of view||75°, 65°, 46°|
|Diaphragm:||f/2.5 - f/22|
|Dimensions||88mm diameter X 122mm long
3.46 X 4.8 inches
|Weight||930g / 32.8 oz (1080g / 38.1 oz for CS version)|
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Wide open at f/2.5, performance is very high over the central 1/2 of the frame, declining gracefully to the corners. The decline to the corners is likely due to field curvature. Stopping down to f/5.6 does improve performance slightly in mid zones, and significantly at frame edge and corners, though the oddball graph confuses the issue.
The MTF charts shows that one cannot expect the same level of performance approaching the edges and corners as with the 70mm f/2.5, at least not on a planar (flat) subject. But it is stil a very high level of performance overall, and real performance might actually be higher, just not on a flat plane of focus.
Mouse over to compare f/5.6.
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