[Leica] Gigabit continued

["Erwin Puts" <imxputs@knoware.nl>]

One of the interesting aspects of this film is ots high resolution: after
several trials I got 150 to 175 linepairs/mm. I used the Apo-Telyt 3.4/135
and a testpattern which among others had small objects (lines and circles
and more complicated figures). The chart was photographed at 4 meters
distance and this film/lens combination gave details that on the negative
were a mere 0.003 mm. That is 3 micron. Can you image how close two details
are that are separated by a three thousands of a mm? At this level it is
most difficult to make observations that are absolutely sure, as the margins
are so small. To be on the safe side. let us go for a resolution of  120
line pairs/mm, that is details of 0.004mm. Not a big improvement, you might
think, but in this type of analysis, it gives a safety margin.
We know that the eye can resolve at best, under ideal circumstances, 6
linepairs/mm. Given the large differences between individuals, most
handbooks go for 3 linepairs/mm as an average.  How much do we have to
enlarge to see these minute details in the negative. For the high figure it
would mean 20 times and for the lower figure 40 times.
Most darkroom workers will have noticed that the jump from 10 times
enlargement to 15 times or higher, induces a severe loss of contrast (the
lens cannot handle it, the enlarger light is spread out over a larger area,
giving flare and reduction of micro-contrast). The definition of very fine
detail automatically suffers.
In this case we are glad to have a high contrast Leica lens, as this
degradation can be  limited. The Focotar however has to be changed as the
Focotar cannot handle these bigger enlargements.
Consider this: at 10 times enlargement the eye can detect details that on
film are between 30 and 60 linepairs/mm. Anything smaller than this limit
cannot be seen. A solid black or grey dot may be indeed a dot or it may
contain micro structures. At 20 times (or better at 40 times) the solid dot
shows even smaller detail and we see details in the details. With a lesser
camera lens the enlargement would indeed show no further information, the
black dot stays black and will be somewhat larger.
This state of affairs does also indicate that testing lenses when done at
moderate enlargements (10 to 15 times) may not be representative of the true
image performance.
Some pople will argue that they never go beyond 10 times, so any additional
information capacity is useless. This at first sight makes sense. But if we
use an analogy from music, we know that music sounds better if the low and
high tones that we may not be able to hear are present, adding to the volume
and richness of the sound. The same works for film. You may not see the
details, but you may sense that there is a hidden dimension beneath the
surface and indeed, when enlarging more, the information pops up.
Optical performance along the whole line of spatial frequencies is more or
less linear: if a lens is good at recording the fine details, it is
automatically less good at recording even finer structures. But the reverse
os true too: if a lens is excellent at recording very fine structures, it is
automatically outstanding at the definition of fine details. So the better
lens  may have an information capacity that exceeds normal expectations, but
you get, as a bonus so to speak, excellent image quality at the level of
perception we habitually use. AND you have the ability to go successfully
beyond the self imposed limits.
There is a persuasive argument, that goes along the line that what was good
enough for Cartier-Bresson should be good enough for us (technically
speaking). Here I wish to disagree. HCB and other masters of 35mm
photography brought us a new vision and greater perceptual awareness of the
reality around us.
Our technical capabilities have been improved significantly and now we can
define our own view of the world ith our enhanced recording capabilities and
I think we should try to do this. Explore new worlds as  Trekkies would have
it. We can get stuck in just proving that it can be done or we may integrate
high resolution photography into a new type of imagery, where all aspects of
contrast, fine grain, high definition and full tonality will be supportive
of our visual language statements.

Erwin