At 16:26 12/22/01, Mike asked:
> .....The best among them all is the fourth, a 50/1.2, which IMO is the
overall
> best of Olympus' 50mm OM lenses. All four are, overall, better than the
> 50/1.8 F.Zuiko I used to own....big snip
>
So where do the 50mm macros fall in this scheme? Specifically the 50/2?
Assuming use as a normal toward the infinity end. In other words do I
get the razor sharp, acceptably fast normal and a macro?
Mike
A reasonable question. I consider the 50mm macro lenses apart from the
"standard" ones because they are designed for much closer
focusing. However, they can easily be used for non-macro, general
photography . . . albeit the speed of the 50/2 is more amenable for it
(only 1/3 stop slower than the f/1.8 lens; the f/3.5 is one-third stop
slower than f/4).
Since I've never owned or used either of them perhaps someone who has used
these and the standard 50mm lenses can comment on their use for general
photography.
Gary Reese's comparison of them is under the 50mm link here:
http://members.aol.com/olympusom/lenstests/default.htm
From his grading the f/2 macro seems to do well at f/4 and tighter. The
f/3.5 seems to do well at f/5.6 and tighter. Gary's testing centers around
MTF (contrast and resolution) plus some remarks about any noticeable
distortions or aberrations. One aspect of a macro in particular is its
bokeh, both in front and behind the depth of field boundaries. A
particular lens design can behave differently in each region although for a
"normal focus range" lens we tend to think about behavior behind the DOF.
"Normal focus range" is from infinity to no closer than *approximately* 8X
the lens' focal length (subject to lens distance). There are technical
reasons for this. As a lens is focused from infinity to some closer
distance, its image circle grows. This results in light falloff at the
film plane and changes the lens' "effective" aperture. This effect is not
very significant until focus distance from subject to lens becomes shorter
than about 8X its focal length. This is the reason an 18mm lens can focus
much closer than a 300mm lens (aside from the immense helical required to
extend a 300mm far enough from the film plane to focus to 0.25 meters).
Macro lenses should compensate for the light falloff effect as part of
their design. IMO it's one of the reasons they are slower and is the most
readily noticed design trade-off. How many other aspects are compromised
(if any and how much) to keep a constant effective aperture and a flat
field (very important for copy work) are specific to a particular lens design.
-- John
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