Re: Drum vs Flat-bed scanners
Re: Drum vs Flat-bed scanners
- Subject: Re: Drum vs Flat-bed scanners
- From: Henrik Holmegaard <email@hidden>
- Date: Sat, 1 Sep 2001 23:24:56 +0200
"Ernst Dinkla" <email@hidden> wrote:
I always thought that it was mainly the better PMT sensor that
made the shadow readings better.
The PMT approach uses an optical lathe and the light is perpendicular
to the X-Y co-ordinate you are scanning. The CCD approach uses an
array of tiny eyes that do not see the X-Y co-ordinate at the same
angle.
The Imacon approach is based on eliminating the glass between the CCD
and the film. The idea is that you eliminate the effect that the
eyes across the array look see the color of a spot on the original
differently due to the effect of the glass. ScanView maintains that
with good optical glass this has a neglible impact. I did an article
with the Imacon and ScanView developers back when Imacon was a
start-up.
One of many dimensions of this discussion is that if you scan a black
dot on an expanse of white, the PMT approach gets you a black dot and
the CCD approach cuts into the black dot and gives you something
lighter as multiple eyes across the width of the array and not a
single perpendicular eye are looking at it.
This is a long and complex story, and in my view the impact of the
software has as much or more to say on the quality you get than the
hardware arguments.