Re: [Leica] By the light of the Leica glow...

[Godfrey DiGiorgi <ramarren@bayarea.net>]

>> With the Elmarit-M 90/2.8, it's a piece of cake: the
>> rangefinder has more than enough baseline to focus
>> that lens to greater accuracy than is required.
>
>Does this lens work with the camera as is (no extra viewfinder or anything)?
>I'm not familiar with the longer focal lengths.

Yes. The standard .72x finder supports framelines for 28, 35, 50, 75, 90 
and 135mm lenses. I find the 135mm framelines too small and the 28mm 
framelines a bit too far to the edge of the viewfinder field for me to 
see them readily and use them for accurate framing. But the 35, 50, 75 
and 90 framelines are reasonably sized and quite accurate. 

Focusing with a rangefinder is like focusing with anything. You need to 
practice enough to become confident and stop fussing over it. Then it's 
smooth and fluid. I spend about 1/30 of a second focusing my lenses and 
the results are very well focused, usually right on target if I was 
thinking clearly enough to understand what my target was. 

>> ... it measures the light in precise accordance with
>> the sensitivity pattern ...
>
>Which reminds me... since the white spot is on a flexible curtain, does 
>the spot ever crack, fade, or wear out?

I suppose it can, eventually, but I've seen M6s around for 18 years or so 
with no such signs of deterioration. Shutter curtains do eventually wear 
out and require replacement. I presume I'll be much older and much grayer 
before I need to start worrying about it.

>With perfect vision, you can see about 2600 picture elements horizontally 
>in a 4x6-inch print, at ten inches. ...
>Unless you look at picture albums with a loupe, worrying about resolution in
>this context is a waste of time.

Ask any optician or opthalmologist: the standard reference for 20/20 
human vision at casual reading distance (10-16" distance) is that we can 
distinguish a spot of approximately .001 inch diameter. This is the basis 
of all standard photographic depth of field table calculations as well. 
.001" spot size is .0254mm, so 20/20 human vision can see appoximately 20 
lp/mm unaided at normal reading distance. 

These are not "picture elements" because human vision is not a digital 
acquisition system. But using the notion of spots as pixels analogously, 
about 4000x6000 spots will make up a maximum sharpness 4x6" print to a 
level indistinguisable without magnification. The same spot size works 
for an 8x10" print, since we tend to view an 8x10" print at about the 
same distance as a 4x6", so a maximum sharpness 8x10" print is comprised 
of about 8000x10000 spots. 

(The perceptions of sharp vs unsharp, however, has only little to do with 
the number of perceivable spots, one of the misleading 
pseudo-contradictions of human perception.)

Your eyes may only see 2600 picture elements in our hypothetical 4x6" 
print's edge (BTW, which dimension did you consider "horizontally"?), but 
I can see up to 4000x6000 spots. I'm glad I have my eyes...

>You're also forgetting everything else.  Scans preserve a lot more of the
>dynamic range than prints; they more closely approach transparencies than
>prints, in fact.  As a result, a scan looks a lot nicer than a print, 
>overall.
>Prints look exceedingly flat, compared to scanned film.

If you say this, it's obvious that you've never seen a well-crafted 
print, mounted and lit properly for viewing. A beautiful print lit 
optimally glows with subtle shadings and tonalities that the best digital 
imaging system can only make a passing gesture of simulating... 

Digital scans displayed on 24bit/pixel computer monitors use an 8bit word 
per red, green and blue channel to represent 2^24 (16,777,216) possible 
simultaneous colors. While this is certainly a very large number allowing 
your eye to be fooled into perceiving a continuous spectrum from the edge 
of visible red to the edge of visible violet and at all intensities from 
black to white, it's a very limited fraction of the infinite tonalities 
available in the analog medium. The quantization limit on a 24bit output 
scanner is 256 levels of intensity for each color or, with a 48bit 
scanner 65536 levels of intensity for each color. The former number is 
nothing compared to the analog medium's infinite tonality scale, the 
latter is larger but is still nothing compared to infinity.

A projected transparency or a well-crafted color print will have far more 
variations in shading than any scanned image on a computer monitor can 
possibly have, an infinite amount more as a matter of fact. Even a 
monochromatic image in the analog medium will have an infinitely greater 
number of shadings than the best digital color print can have, even 
theoretically. Infinity minus 16,777,216 leaves an equally sized infinity 
behind, Anthony. It's simple mathematics, one of the fundamental theorems 
of large numbers. Digital systems are easy to work with because they have 
simple, well-defined, discrete limits. Analog things are difficult 
because they have infinities to manage.

The happy thing is that the eye is fooled easily and we can be satisfied 
that our eyes are tricked into appreciating a rather constrained digital 
image as if it were an infinitely variably toned analog print or 
projected slide. But put them side by side and the analog medium has an 
obvious advantage in its subtleties. 

BTW, going back to my original statement:
 >The quality of the Leica lenses is
 >evident even in junk-one-hour photofinishing 4x6 prints ... I think I 
can
 >spy the weak force at work at the subatomic level in there. 
I didn't mean to imply that the one-hour prints were anything but cheap 
prints to look at. The intent of the statement was not to get into a 
debate as to the qualities of analog vs digital images but to say that I 
find the quality of the Leica lenses to be evident even in a cheap print 
from a photofinishing lab, in a humorous sort of way. 

I suspect that the other LUG members would be grateful if we moved this 
discussion off-line from their regularly scheduled debates of plastic vs 
metal, finish qualities, M3s vs M6s, etc. So if you would like to discuss 
imaging, imaging systems, etc., in further detail, please let's do so on 
our own time in private email. I have an extensive professional career 
behind me working in imaging systems (analog and digital, electromagnetic 
spectra from the visible and beyond, coherent and chaotic image 
processing algorithms, pattern recognition, the design of custom 
machinery for digital processing, etc.) and enjoy the discussion 
immensely. There is much to be said for the interplay of ideas that we 
may both learn a little more. 

best,
Godfrey