Re: [Leica] 50 mm M lens comparisons (long)

[Erwin Puts <imxputs@knoware.nl>]

>Erwin & others,
>
>I hardly understand all your arguments on Leitz's/ Leica's
>50 mmm M lenses, which take one aspect only into account most of
>the times.
>
>But, the stuff that really annoys me, is that the differences
>between Leitz's/Leica's 50 mm M lenses are almost as strong as
>between different focal length - and hardly anyone cares for
>the differences.

Hello Alf,
You are right is stating that the differences between the several
generations and types of Leica 50mm lenses are quite large.
The characteristics you list and appreciate, are all different
manifestations of one basic fact: less rigorous optical correction for the
various aberrations of lenses.
These characteristics may be interesting for historical reasons, they may
appeal to nostalgic feelings and they may be used to good effect for
producing images that one can admire.
Bottom line is that modern lenses are corrected to a high degree and
therefore the phenomena you list do not longer exist in modern lenses.
It is also a matter of fact that the characteristics we have been
discussing in this thread (sharpness, contrast among others) can be used as
a proxy for other optical parameters. A lens that has high contrast and
excellent rendition of fine detail MUST have suberb flare reduction and
good separation of highlight and shadowdetail. Otherwise it could never
exhibit this fine performance.
So we are not forgetting to mention some characteristics, but the aspects
you refer to are included in the overall qualification.
To give some perspective:
Any lens should ideally be evaluated on all these points:
distances of 0,7m, 1m, 3m, 5m, maybe 10m and infinity;
image points at center and 3mm, 6mm, 9mm, 12mm, 15 and 21mm radius
at all apertures
and for these aspects
spatial frequencies from 60 to 6 lp/mm
distortion
colour transmission
flare
vignetting
out of focus rendition
and many more parameters.

The amount of testing and the number of figures to be amassed and analysed
is simply above anyone's capabilities.

When we talk about lens A being better than lens B we not only should
inform which of the above aspects we are referring to and try to quantify
it. We should also be very carefull not to mix up the measurements of these
aspects with our subjective appreciation of it.

I do not think that there is any photographic situation (not even a high
contrast one) where the modern Summicron would deliver results that the
venerable Summar could do better. Unless you can describe very specifically
what you mean. Your mention of Hollywood portraits is quite appropriate.
Hollywood pictures of the '20, with soft focus and flare may be the
province of the Summar, but Hollywood portraits of the '50, shot with
Rolleiflex and 4x5 inch can only be approached by the modern Summicron.
Erwin