CyberSimian wrote:
>Brian Swale wrote:
>
>
>>I value objective measures such as lines per mm, since the personal
>>opinion factor is greatly reduced and you are getting close to facts.
>>
Good stuff, Cy, but it still doesn't answer Brian's question about macro
performance of the 50/2. Looking at your original post, I see the
conclusion of the review refers to excellent macro, but with no backup
data. The way it's written makes it sound like they may have taken Oly's
word for that part. At least the tests results summarized below raise
some question about the reviewer's source.:
"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."
-------------------------------------------------------------------------------------------
I wrote Gary Reese off line about his comment to me some time ago about
a test of macro. (Embarassingly enough, he referred me to the archives
for his posts in 1998 on the subject. I thought you folks who cared
would have done a little basic research! Shape up out there! :-) :-) )
Well, he did offer something that wasn't missed in the old posts, some
numbers on sharpness at infinity vs. 1:2. Please note that the slower
speed at 1:2 is due to the normal effect of lens extension. I've
reformatted his original to present the 2 side by side.
---------------------------------------------------------------------------------------------------------------------
Here is where I first presented the Popular Photography data:
> >
> > < http://zuiko.sls.bc.ca/~swright/archives/1998/msg02665.html >
> >
> > with a follow-up:
> >
> > < http://zuiko.sls.bc.ca/~swright/archives/1998/msg06049.html >
> >
------------------------------------------------------------------------
The most informative 'lens test I have ever seen on the 50mm f/2 Zuiko Macro
was Popular
Photography's (PP) split image contrast test. For some reason it was left off
the compilation of
PP tests on Lee Hawkins site at:
< http://brashear.phys.appstate.edu/lhawkins/photo/pop-photo-zuiko-tests.txt >
perhaps because an interlibrary loan took so long to get me the photocopy. So
here are the charts
converted to datapoints:
50/2.0 MC (Popular Photography 4/86, p. 106 (w/OM-3 test, pp. 30-3))
Performance at infinity: Performance at "macro" limit:
Actual focal length & T-stop: Actual focal length and T-stop:
52mm f/2.08 40mm f/3.12
Distortion: none Distortion: none
Centering: near perfect Centering: near perfect
Vignetting: none beyond f/4.5 Vignetting: none beyond f/4.5
Flare: 0.44% Flare: 0.44%
Transmission: 95.4% Transmission: 95.4%
(T-stop f/2.18) (T-stop f/3.27)
Percent contrast of 0.01mm slit image:
f/2 f/2
Center 69 Center 60
1/3 out 58 1/3 out 47
2/3 out 50 2/3 out 38
far edge 51 far edge 30
f/2.8 f/2.8
Center 73 Center 68
1/3 out 60 1/3 out 54
2/3 out 58 2/3 out 40
far edge 55 far edge 31
f/4 f/4
Center 80 Center 69
1/3 out 79 1/3 out 60
2/3 out 65 2/3 out 50
far edge 68 far edge 40
f/5.6 f/5.6
Center 84 Center 70
1/3rd out 84 l/3rd out 69
2/3 out 70 2/3 out 55
far edge 76 far edge 45
f/8 f/8
Center 83 Center 77
1/3rd out 84 l/3rd out 71
2/3 out 75 2/3 out 65
far edge 80 far edge 55
Noteworthy are:
* f/8 is the optimum aperture
* performance degrades at close focus limit, perhaps showing that the near AND
far aberration
correction (floating elements) mechanism actually favors near macro distances
(but what
distance???)
* focal length is decreased at close focusing distances, which indicates there
is some internal
focusing going on and probably a reduced barrel extension at 1:2 over what
would occur in a
lens without floating elements and/or internal focusing.
Gary Reese
Las Vegas, NV
----------------------------------------------------------------------------------
Still a good macro lens at 1:2, at least stopped down to f8 and/or with 3D
subjects where the edges don't matter, but doesn't really seem to bear out
Oly's statement "Outstanding performance with extremely stable resolution from
infinity to 1/2 x life size" I'll stick with the 50/3.5 for flat copy work.
Well, I was going to do that anyway.
Finally get what you were looking for, Brian? :-)
Moose
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