Re: Resolutions

From: Andrew Stawowczyk Long (anlong@NLA.GOV.AU)
Date: Wed May 30 2001 - 00:52:46 CDT

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    Message-Id: <200105300552.WAA13982@dns.ccit.arizona.edu>
Date:         Wed, 30 May 2001 15:52:46 +1000
From: Andrew Stawowczyk Long <mailto:anlong@NLA.GOV.AU>
Subject:      Re: Resolutions
To: mailto:IMAGELIB@LISTSERV.ARIZONA.EDU

    <pre> David,

    I agree with your comments on good and bad scanners. I would add, also, another important feature in scanners - low nois
    . As to glass negatives, we had some projects like that and we found out that 2000dpi (regardless of the neg size) gives p rfect results. I suppose you could go lower, possibly down to 1500dpi especially with some negatives, but generally 2000 is good. It creates large files (over 300Mb with 8"x10" in greyscale) but I am afraid we have to cope with it - it will be happening more and more often that we use large files.

    Cheers Andrew Stawowczyk Long Manager Imaging Services Branch National Library of Australia mailto:anlong@nla.gov.au

    David Adams wrote:

    > > ----------
    > > From: David Adams[SMTP:mailto:DAVID.ADAMS@NATLIB.GOVT.NZ]
    > > Sent: Wednesday, May 30, 2001 2:52:23 PM
    > > To: mailto:IMAGELIB@LISTSERV.ARIZONA.EDU
    > > Subject: Resolutions
    > > Auto forwarded by a Rule
    > >
    > 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 t
     10"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 -
    hat 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 equ
    tes 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 800
    pi.
    > (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 th
    n 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 h s 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

    </pre>

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