(Extracted from the February 1991 issue of the UK photo magazine "Practical
Photography".)
This OM 50mm is far chunkier and heavier than its f1.8 counterpart, even
though the maximum aperture is that bit slower. Why? Because this is a
specialist macro optic, focusing down to half lifesize. Such close focus
ability requires extra glass elements in a more complex configuration, which
not surprisingly adds bulk and weight.
The broad focusing barrel must be racked over 300 degrees to move the lens
from its infinity position round to minimum setting. At this point lens
length grows by nearly 50%!
The prime requisite of an optic used for macro pictures is that it should be
sharp as a tack when stopped down. The Zuiko fulfils this criterion with
something to spare. At f2 and f2.8 both edge and central definition kick
off at respectable levels, but further stopping down is like lighting the
blue touch paper. Not only does centre frame boast superb performance from
this point, but edge performance is pretty elevated too -- both figures
comfortably exceed the 70% mark at all subsequent apertures.
So for critical copying and macro subjects where sharpness and depth of
field go hand in hand, the Zuiko is really in its element.
Lens number: not available
MTF % values for centre and edge (edge in parenthesis)
(the spatial frequency measured was not specified):
f2: 50% (48%)
f2.8: 58% (55%)
f4: 75% (70%)
f5.6: 81% (78%)
f8: 82% (75%)
f11: 78% (72%)
f16: 72% (71%)
Concluding Summary:
A star performer in this group of Zuiko lenses is the 50mm f2 macro.
Although larger and more expensive than the f1.8, the f2 features excellent
centre and edge definition. Plus it has this remarkable ability to get
close without any fall-off in performance.
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