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[OM] Re: What's so good about the Zuiko 50/2 ??

Subject: [OM] Re: What's so good about the Zuiko 50/2 ??
From: Moose <olymoose@xxxxxxxxxxxxxxx>
Date: Sat, 29 Jan 2005 21:48:14 -0800
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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