[Leica] Information content, 1

[Erwin Puts <imxputs@knoware.nl>]

When testing lenses in the field, one has to add one more variable
parameter to the imaging chain and that is film. So it might be interesting
to know which filmtype (slide or colourneg) and what film generations do
give the highest information content with best fidelity. I took two of the
best lenses for the M (with measurable extremely high recording capacity:
The Apo-Telyt 3.4/135 and the Apo-Summicron 2/90) and selected two silde
and two cneg films.
The first object was an old church front with a very elaborate group of
colourful motives (saints and ornamental decorations in mosaic stone
pattern. The stones ae very tiny). The church buiding had very withered
stone masonry with rough and extrenely fine textures.
The Apo-Telyt on tripod and almost at infinity. Church distance about 50
meters.
At 10 times magnification the slide film showed exremely fine detail very
crisply rendered with great clarity. The cneg film showed identical detal,
slightly softer at the edges of the painted lines of the figures. At 30
times enlargement the very fine lines of the mosaic pattern started to show
through the until then smooth painted texture. Still both the slide and
cneg film emulsion recorded the image details very faithfully. At 100 times
magnification the grainpattern of the slide film became clearly visible,
but the details still visible. The grainpattern showed high acutance which
helped preserve the fine details. Of course the subject outlines of
exceedingly fine detail are a bit soft now,but all information is still
detectable. The grain structure now has a higher noise level and fine light
and colour modualtions are not recorded anymore. The grain (better: the dye
blotches) of the cneg film are smaller, but now there is a fine trade-off:
outlines are softer and become fuzzy, but subtle gradations are a bit
better preserved as the noise level is lower.   The slide film however has
the crisper image and a higher sharpness impression.
The upshot: when enlarging the information content grows and is recorded
with true fidelity till about 100 times. A tribute to the lens of course.
It also shows that the optical cababilities of the newest Leica
lensgeneration now are better than the filmemulsions can record.It also
shows that the recent filmemulsions are superior in information recording
potential to older generations of lenses.

to be continued

Erwin