Message-Id: <200105300453.VAA30180@dns.ccit.arizona.edu> Date: Wed, 30 May 2001 16:52:23 +1200 From: David Adams <mailto:David.Adams@NATLIB.GOVT.NZ> Subject: Resolutions To: mailto:IMAGELIB@LISTSERV.ARIZONA.EDU
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Interesting discussion on resolutions.
Which raises a question I'd like to throw to the 'thread'...
We are investigating a large scale digitisation project of glass plate negatives (GPNs) of all sizes from 1/4 plates to
0"x12", a total of 140,000.
The project is to span over a period of more than 5yrs.
I am researching info for the specification of resolution and quality
(currently we have been scanning GPNs for 6 yrs and we initially put a stake in the ground of 8 megabytes per image - th
t was a respectable file size in 1995!)
At the moment I am considering that a scanned image would have a minimum of 5,000 pixels on its longest edge, this equat
s at about 20Meg for any given plate size
or....
There is the philosophy that no matter what the GPN size, it should be scanned at the same resolution, for example 800pp
.
(This stands to reason, a 8x10 neg has a lot more information than a 1/4 plate)
But of course a 10"x 12" GPN at 800ppi is very large file size - 100Meg+ at a guess.
The question is
What approach are other projects selecting?
PS
One point that no one has mentioned
an average quality scanner used at its highest resolution is not necessarily going to produce a better quality scan than
that of a very good quality scanner at a lower resolution - i.e. I'd rather produce a 12 Meg scan that is sharp and has
a good dynamic range than say a 40 Meg soft scan with clipped shadows and highlights.
David Adams
Team Leader Copying Services
National Library of New Zealand
+64 4 4743151
Visit "Timeframes" New Zealands leading source of heritage images
http://timeframes.natlib.govt.nz/
www.natlib.govt.nz
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