Re: [Leica] Summicron report part 2

[Erwin Puts <imxputs@knoware.nl>]

Some physical measurements to show the difference between Collapsible and
Rigid/DR:
frontlens of the C is about 2 mm smaller in diameter than the R/DR, but the
rear lens is about 1 mm larger. From bayonet flange to front the C is
39,2mm and the R/DR is 43,5mm. The rear element of the C is is almost flush
to the flange while the R/DR is recessed about 5 mm.

Optical progress between the earlier first generation Summicron and the
latest one (not the last one: a new version will someday be available)
shows stunning results. Has the user accomodated to these new heights of
image quality?
First of all I did not find any relation between the overall optical
quality and the maximum resolution figure, still sometimes used as a
yardstick to image quality. Well it is not. The Summicron 3gen has a lower
value here than the Rigid one, but a much higher level of image quality.
Secondly I noticed that in many out-of-pocket picture taking and even some
serious tripod work of high contrast scenes, that the Collapsible held its
own better than would be expected from the figures and measurements.
Look at the figures for a circular zone about 2 mm large at a distance of
about 8mm from the center. Here the C is a little unsharp, fine details has
very soft edges, the very fine details are sagitally and tangentially
different because of astigmatism, but anyway again very soft, extremely
fine details are hardly visible and even finer structures are not recorded.
On film only the fine details and outlines will be visible, the rest will
be below the grain threshold and will not be recorded, at least not with
film-emulsions of the '50s.
The same spot for the R/DR shows some flare and low contrast and also
astigmatism but less as with the C. The very fine details are sharpish, but
not crisp, and extremely fine detail is soft. Exceedingly fine detail will
be lost in the grain structure and is hardly visible.
The new Summicron has a high contrast image here, no trace of flare and
astigmatism, extremely fine detail is very crisp and even exceedingly fine
detail is rendered clearly, but beyond the capablity of most film/users.
Given these figures we can assume that even for high quality pictorial work
the rendition of fine detail and especially the outlines are instrumental
for the overall image quality. We do not see the several aberations
separately. Most aberaations generate soft spots ansd some will change
shapes of spots (coma as example). So the result of taming the aberations
is a crispening of very fine detail over the whole image area.
It were the Japanese who noted that a very nivce sharpness impression could
be conveyed by optimizing the outlines of details, that is the 5 lp/mm
threshold. Yes that is true, most photographic optics are not required to
produce more than 5lp/mm or at most 10/lp/mm. Here we note (see an earlier
post) that modern emusions have a MTF of about 100%.
Now we can understand why older Summicrons still perform so well: the 5 and
10lp/mm limit is very acceptable and should have been in the early '50s a
revelation. Especially the evenness of performance over a large image field
is important.
We can now understand why so many persons can hold to the statement that
Nikon. Canon. Pentax produce very sharp pictures. These lenses are
optimized for exactly these structures.
In practical situations we are not using the full potential of the modern
Leica lenses (maybe the effort to get the most out of them is too high a
price to pay, but why do we pay the hefty amounts of momey for Leica glass)
and as long as we go on exploiting the fine details limit and dare not go
further, some revelations will not be discovered.
It is perfectly legitimate to have personal lens-acceptance-procedures as
are reported now on the LUG.
Many of the finer points of Leica quality will not be revealed in this
procedure.
The sparkling clarity of the finest details, rendered crisply and finely
graduated  with excellent colour neutrality is an everlasting joy and quite
addictive: once you noticed it, you will not settle for less.
But then the Leica M has more uses: photojournalists and other
professionals will look for different criteria.
Erwin