Dawid Loubser wrote:
> That makes sense. I've never used a 40/2.0 (would love one) but symmetrical
> designs generally produce great background blur, and the 40/2.0 is one of the
> few (if any?) OM Zuiko fully symmetrical lens designs?
The 40/2 is no more symmetrical than the various 50 mm lenses.
<http://www.moosemystic.net/Gallery/tech/Lenses/SECT-HORIZ.jpg>
The 40 mm and all the 50s, and indeed essentially all 40-58 mm pancake &
normal FL lenses for 35 mm SLRs & FF DSLRs, are variations of the
double-gauss design. Those faster than f2.8, depending partly on price,
usually have an additional element. Thus the 7 element 50/1.4 & 1.2 Zuikos.
The economy 50/1.8 is 6 element and the 50/3.5 macro is slow enough to
get by very well with a single element rear corrector lens. The 40/2 was
an inexpensive lens when introduced. The 6 element design is probably
partly to reduce cost and partly to reduce size. It's also the reason
for it's slightly less than first rate performance, I'd guess.
Pancake designs by various makers are generally around 40 mm for the
simple reason that that is as short as a non-retrofocus, double-gauss
design can be made within register distance and mirror clearance
constraints.
Moose
> Though the dedicated Macros (80 and 135) are also pretty symmetrical if I
> recall correctly, hence their good performance in the bokeh department.
>
Yup, both double-gauss.
> I wish we could put together one nice database (suggested last year sometime)
> of sample images made through all zuiko lenses.
>
This is far more ambitious a project than you might imagine. The problem
is that bokeh is significantly affected by both focal plane and
background distances and perhaps by the ratio of them..So the number of
test shots required is considerable for each lens.
Moose
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