> I've never seen Clark's stuff before and it will take a while
> to digest. However, the comparison on Luminous Landscape was
> to Provia 100F and not Velvia. According to Clarks graphs
> the Provia has luminosity resolution up to 12MP but the color
> information is only good to 7MP.
How is that any different than the three-color array in our
sensors. In theory, the luminosity resolution of a 6MP camera is
6MP, but the color information is only 3MP. (2 pixels to define
one color) or even 2MP (3 pixels to define one color)? If I'm
really generous with the algorithm, it's no better than 4MP.
Clark's comparison matches my own tests. I know, from careful
testing, that digital appears to be sharper right up to its
maximum resolution where the detail blocks up. With film, the
apparant sharpness is lower due to various reasons, but mostly
because the grain/pixel contrast is lower. Apply a
noise-removal algorithm and a bit of USM and things start to
match up better. At the granular level, colors and densities on
film aren't as intense as they are in digital. Does this make
one resolve better than the other? Not really, but to the eye
the difference is huge.
Which brings up a point that I've been wanting to express:
A scanner is a digital camera. Film is the scene being
photographed. If you adjust your scanning techniques to match
how we achieve the best (noise-free) images from a digital
camera the scans will improve. This includes "expose to the
right". It also includes getting the contrast color as close to
perfect during the scan as possible too. Here's my
recommendation:
Using Vuescan (every person with a scanner should have a copy of
Vuescan), turn the color/brightness adjustments off on the color
tab. On the first tab, adjust the "Exposure" settings there till
you have a full-range image as very close to the desired
brightness as possible. If you are not needing to protect the
highlights, crank the exposure up so all of the curves are well
placed above the black point. Only after you get the exposure
level as close as you can get it do you turn the color
adjustment controls back on.
Ok, back to film...
Is there a resolution difference between Velvia and Provia? On
what planet does anybody think the two films are basically the
same? They are NOT the same. The original Fujichrome 100 was
an incredibly sharp film, but had a coarse, sandy grain. Provia
replaced that with a slightly less sharp, but softened grain
which had the APPEARANCE of being less grainy therefore sharper
image. Think of M&Ms that have been melted down--the individual
candies have lost their round edges (therefore cleaner grain),
but at the same time the absolute resolution is lost. Velvia
100F has also lost the course look for a more blobby
characteristic. But it DOES scan cleaner with less grain
aliasing.
AG
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