Lars Bergquist wrote:
Thanks Lars !
That discussion was very good but I was experiencing "circles of
confusion"
and did not want anyone to become polarized (circularly, ofcourse!) on
the
issue of sharpness. I was hoping you would straighten us out.
Know that I delight in your concise treatises on photographic matters,
and
that I have hidden away my green filter in the furthest recesses of my
camera
gear bag! If you convert this to HTML, please let me know!
Wrote the Badger from flash powder days:
>
> A) Sharpness in the plane of focus in subject:
> 1) Resolution. Lines per inch or millimeter. A function of cameraman
> (holding, tripod, good focusing), camera (film flatness,
> adjustment and
> focusing aids in finder), lens quality and film emulsion (coarse
> grain =
> low resolution).
> 2) Acutance or edge sharpness. The abruptness of change from dark to
> light
> or from one color to another at a subject edge. Mainly a function
> of the
> emulsion (thin = better) but can be influenced by development,
> e.g. in
> a dilute developer with still periods between agitations--but it
> presupposes
> good resolution in the first place!
> 3) Contrast transfer (MTF): does fine detail hold contrast or does it
> go flat?
> This is mainly a question of lens quality (if 1 and 2 are present).
>
> B) Experienced or subjective sharpness. Heavy stopping down can create an
> impression of great sharpness because more is in reasonable
> focus--but
> sharpness in plane of best focus decreases beyond mid-stops
> because of
> increased diffraction around edges of diaphragm blades. Also,
> high contrast
> subjects and contrasty printing can give rise to a false
> impression of
> sharpness. And coarse and sharp grain can mask an inherently
> somewhat
> unsharp optical image, as I pointed out previously.
>
> Each point above could be the subject of a chapter in a book---or even a whole
> book! However, if we try to be clear about what we are talking about, much
> misunderstanding will be cleared away.
>
> Vänliga hälsningar/Best regards
> Lars Bergquist
> Välkommen till/Welcome to ...
> <http://www.bahnhof.se/~timberwolf/>
>
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