The very nice website that Piers posted mentioned using a 48 micron aperture
to measure RMS granularity. Aren't pixels as small as about 8 microns?
That 48 micron aperture would average 5 or 6 pixels. I guess the key is that
they say they multiply the density variationr by 1000 to get a whole number
implying the variation on film for different 48 micron spots is a fraction
of 1%. If the eye could see the random variations on spots 48 microns in
diameter, that would appear quite grainy. It would be interesting to see the
film density variation with say a 10 micron aperture
-jeff
----Original Message Follows----
From: Winsor Crosby <wincros@xxxxxxxxxxx>
I think Reichmann's point was that even though grain is about half
the size of pixel sites it is either black or white. He said you need
a little group of grains to make gray and that clump is bigger than a
pixel which can be several thousand shades of gray in its discrete
little self. I think he was trying to show why comparisons that use
black and white resolution charts give an advantage to film that is
not reflected in real world photography. Thought provoking stuff.
Winsor
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