(Extracted from the February 1991 issue of the UK photo magazine "Practical
Photography".)
The f3.5 is one of two 21mm superwides featured in the range -- the other is
a speedy f2 model. This f3.5 version is a mere 31mm long, which is as tiny
as Zuiko's standard lens. So there is just enough room on the short lens
barrel for the rubberised focusing grip and slim aperture ring -- but no
more. Despite the proximity of these two, their raised surfaces permit even
a gloved hand to operate each cleanly and independently.
Focusing down to 0.2m is accomplished in a beautifully smooth 90 degree
turn, while the aperture ring has firm click stops at whole aperture
increments. Despite the sweeping 92 degree angle of view, the lens' front
element is modestly sized so it accepts the 49mm filters common to many
Zuiko optics. The depth of field indicator, marked here at f3.5, f8, and
f16, is a clear and welcome feature of all OM system optics.
So far, so good, but how does this small superwide fare optically? As our
MTF graph reveals, central definition starts off at a very high level at
full aperture, and climbs to an impressive peak once stopped down to f5.6
and f8. Though performance tails off from that point, the smaller apertures
also show healthy levels of contrast.
The edges, though hardly down in the doldrums, never approach the consistent
excellence of centre frame. Full and minimum apertures manage good ratings,
while the middle settings claw their way up around the 50% mark. So crisp
centre frame detail is available at any aperture. But if critical edge
sharpness is required, as in a broad landscape scene, it's advisable to use
a mid-aperture setting.
Lens number: 120880
MTF % values for centre and edge (edge in parenthesis)
(the spatial frequency measured was not specified):
f3.5: 70% (41%)
f5.6: 83% (50%)
f8: 76% (48%)
f11: 66% (43%)
f16: 59% (40%)
Concluding Summary:
The 21mm f3.5 has much going for it. It boasts tiny dimensions, sweet
handling, and decent levels of definition, especially in centre frame.
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