Archived posting to the Leica Users Group, 1998/01/23

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Subject: Re: Re[2]: [Leica] S'cron performance
From: Erwin Puts <imxputs@knoware.nl>
Date: Sat, 24 Jan 1998 00:12:04 +0100

>The question goes back to Leica design.  Do they design for high resoultion?
>Do they design for high contrast?  Micro details seems to simply be a
>description of high resolution and contrast.  Am I incorrect about this?  Does
>micro resolution mean something else?
>
>Tom Shea

I assume that micro resolution means the resolution of microscopic details.
You can have good contrast at fairly high spatial frequencies (about 50
lp/mm: to be clear: a linepair is one blackbar and one adjacent white bar).
High resolution has no clear meaning: in wafer optics 5000 lp/mm are high
resolution, in photography 100lp/mm are counted as high res.
The posting giving figures of 400lp/mm for a Leica lens must be surely have
been misread or misquoted.
Leica lenses are designed for high contrast AND high resolution to the
limits of usable visual information. It is impossible to have a lens with
200lp/mm and good contrast. A lens with very high resolving power beyond
the limits of film resolution and the capabilities of the eye has worse
quality than a lens with a somewhat lower resolution.
Leica lenses therefor have a fairly sharp cutoff spatialfrequency, implying
that is much better to have NO resolution beyond this cutoff point than to
have some resolution beyond this point as this resolution will degrade the
contrast and therefore the imag qualities as a whole.
As modern optical thinking has it nowadays, a very high resolution figure
means automatically a design that is not optimized for optimum photographic
quality as it is interpreted these days.
The classical statement that Leica goes for smooth gradation and Japanese
lenses go for contrast has never been true in the past and is not true now.
To bring some perspective: most Leica lenses used by almost all people are
being used in circomstances where 20 lp/mm are a very high target.
So let us for once forget about resolution figures because maximum
resolution is not the  qualifier we need to discuss image quality and
optical performance.
Erwin