To take this one step further and define MINIMUM film scanner resolution
that begins to capture what Velvia is capable of delivering:
Divide Nyquist Limit by Kell Factor . . .
2 / 0.7 ~= 3
Since 81 lp/mm requires two pixels to create a line pair . . .
81 lp/mm * 3 = 243 pixels/mm
Therefore, a film scanner requires a MINIMUM of approximately 240 pixels/mm
optical scanning capability (NO interpolation allowed!!) to be on the brink
of capturing the information content Velvia contains.
Work this out to a 35mm film frame and the resulting digital file must be
8640 x 5760 pixels. Furthermore, NO lossy compression schemes are
allowed! There's also color gradation, or for B&W a digitizing of the
grayscale.
Am I ready to go digital yet? Nope, not me. Am I ready to commit my
Kodachromes to CD's and ditch the slide archives yet? Nope, not me. For
all these reasons and more . . . such as the archival life of CD's
(especially those burned at home), and the rapid sunsetting of digital
storage media and technologies.
-- John
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