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Re: scanning alt prints
In a message dated 3/3/00 4:53:29 PM Eastern Standard Time,
cweese@earthlink.net writes:
> BUT, my ten year old Microtek
> appears incapable of delivering the same tonal map two scans in a row.
Hi Carl,
There are at least 2 different problems that can affect consistency. One is
the repeatability where you get different values even if you scan the same
image, same area, and the other one is what they usually called "hot spot" or
"hot spots" where different area of the scanner gives different values.
You can check repeatability by scanning the same section several times and
compare the scans. If you want to check into details, you can place 2 scans
into 2 different layers and set the mode of the top layer to "difference" (or
place into 2 different channels do a channel subtraction). Theoretically you
should get a black screen (value = 0) as the result, but some small
difference of course exist due to normal variation and noise. If
repeatability is a problem, then you probably need a repair or as you said, a
new scanner.
If repeatibility is not a problem, then you probably get hot spots. In that
case, if you don't want to get a new scanner, you need to make sure that the
joining area is on the same section when you scan; that is, after you scan
the first section, instead of just moving the image, you need to flip it 180
degrees to place the joining area in the same place. Then of course you need
to rotate one section back in Photoshop.
Another factor is usually the scanner has a frame around the glass. When you
place your image on the scanner, it is flat against the glass in the middle
section, but at the edge, the print is raised just a little bit because of
the frame (although it is thin, probably just 1 mm), but it causes a density
difference. So you want to make sure the joining area is at least about an
inch away from the edge.
> So, while this is getting a little off-subject for alt, since I know
> some of you are doing similar things, is the inconsistency from scan to
> scan just a problem with my "antique" scanner that a new-tech model will
> solve? What equipment are folks using that delivers segmented scans with
> consistent tonal values?
I use Arcus II, but I believe many scanners can do the same thing nowadays.
Hope this helps a little, and sorry if what I said is not applicable. Your
original question was brief so I don't know what you have tried/checked.
Dave Soemarko
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