Re: Glass slide imaging - Optical Range is important

From: David Adams (David.Adams@NATLIB.GOVT.NZ)
Date: Tue Aug 22 2000 - 16:38:34 CDT

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    Message-Id: <200008222143.OAA20518@dns.ccit.arizona.edu>
Date:         Wed, 23 Aug 2000 09:38:34 +1200
From: David Adams <mailto:David.Adams@NATLIB.GOVT.NZ>
Subject:      Re: Glass slide imaging - Optical Range is important
To: mailto:IMAGELIB@LISTSERV.ARIZONA.EDU

    <pre> I have been trying to identify a good scanner for our Library Image Services Unit, and one of the criteria for choosing t will be its ability to scan glass plate negatives (Our glass plate collections are 1/4 plate up to 12"x16") We have been using an Agfa Horizon+ flatbed scanner, this has been quite effective but is now 4yrs old and in need of an upgrade. I am now on the lookout for a good scanner to meet these needs, and have asked other users what works well for hem. The problem with most flatbed scanners is that they have 'drawers' for holding transparent objects which are not appropr ate for glass plates or unusual format sizes.

    The capture resolution is just one important specification but one specification not to over look is Optical Density or ensity Range this is the real performance feature to look for in a scanner.
    (in general terms this is its ability to scan and render the most dense part of the image)

    When looking at scanner specifications this will be recorded as a figure for "Range" or "Dmax" For a scanner with excellent optical density the Dmax will be close to 4.0 and the Range 3.7, this would be a scanner in the professional range. (Drum scanners Have an excellent Dmax figure, but not for glass negs obviously!) Naturally the optical density is directly proportional to the cost of a scanner - the higher the figure is the higher th
     cost. Cheap scanners often will not include optical density in their specification, probably because it would be embarrassing.

    Choosing a scanner will probably be budget related but I would be looking for an optical density of at least 3.3 or more

    The "ScanMate" range has been recommended to me from one user because it uses a mounting plate that holds the glass plat s with care (and has an optical density range of 3.7)

    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/

    >>> mailto:elevine@UNIDO.ORG 08/22/00 01:22 >>>
         Dear Colleagues,

         I have an urgent requirement for information about scanning
         photographs from glass plates. I will need up to 600 DPI. Help.
         Any recommendations for equipment, DPI.

         Thanks in advance.

         Emil Levine

    </pre>

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