[Leica] Digital print quality

[Erwin Puts <imxputs@knoware.nl>]

It is wellknown that the number of dots per inch is not directly related to
image quality. Of course a print with 720 dpi on high glossy paper can look
very convincing. But what of the inherent properties. We know that only
primary colours (that is the colours available in the cartridges) will be
printed at the smallest possible dot size. All other colours are rasterized
and so use more space. Most colours droplets, from whatever technology
(piezo or hated droplets) do bleed and spread out, even on the best paper.
Acutance then is a pipe dream. In reality you get a print quality related to
60lines per cm (152 lpi), that is 6 lines per mm or 3 lp/mm.
We can see details on the print, separated by 0.01inch or 0.2mm. That
happens to be the maximum print resolution, established here. An A 4 size
represents a 8 times enlargement from the negative.
On the assumption that the scanning process of the negative or slide has no
degrading effects, and using the A4 as the print size, we may say that a
digital print of a scanned negative is equivalent to an nlargement of 8
times from the original negative size. The 3 lp/mm on the print than
translate to 25 lp/mm on the negative. That is the maximum information from
the negative that can be reproduced with the digital process. When using A3,
we go to 50 lp/mm, but that is beyond the scanner resolution.
Now leica negatives easliy hold 50 to 100 lp/mm! And optical quality of
Leica lenses is superior to other marques exactly when exploiting the higher
resolutions at the better MTF values. So the cut-off point for the digital
print is exactly at a point where Leica lenses start to show their best
performance! 

Erwin