Message-Id: <200011070436.VAA24026@dns.ccit.arizona.edu> Date: Tue, 7 Nov 2000 15:33:57 +1100 From: Andrew Stawowczyk Long <mailto:anlong@NLA.GOV.AU> Subject: Re: Researching scanners - and colour depth To: mailto:IMAGELIB@LISTSERV.ARIZONA.EDU
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Most popular software is not able to manipulate images higher than 24-bit. Many programs can open
them, though. Scanning and storing images at higher bit-depth than 24 is beneficial especially for
source material that has greater tonality range or is difficult to read
(faded manuscripts, photographs). However, storing and using images with higher bit depth is time
consuming and expensive. It seems that currently most material is stored at 24-bit but scanning has
to be done with at least 36-bit depth as it permits to capture entire
tonal range of the original. It is particularly important for scanning colour film - eg. information
in colour negatives is highly compressed and only scanners with high bit-depth capture can extract it.
PS. I hardly can believe in Atixscan to have 4.0D dynamic range. Methods of measuring dynamic range
are subjective designed by scanner manufacurers - ther are no objective standards. 4.0D is the
absolute theoretical maximum - really impossible to achieve.
Andrew Stawowczyk Long
Manager
Photographic Services
National Library of Australia
mailto:anlong@nla.gov.au
David Adams wrote:
> > ----------
> > From: David Adams[SMTP:mailto:DAVID.ADAMS@NATLIB.GOVT.NZ]
> > Sent: Tuesday, November 07, 2000 6:45:51 AM
> > To: mailto:IMAGELIB@LISTSERV.ARIZONA.EDU
> > Subject: Re: Researching scanners - and colour depth
> > Auto forwarded by a Rule
> >
> I have been researching scanners recently and just learnt that Microtek are releasing a newer model called the Atixsca
1100, which is physically the same as the ScanMaker 5 but has a higher dynamic range, this is 'claimed' as being 4.0Dma
(the ScanMaker 5 is 3.6Dmax)
> It is also 42bit (14bits per pixel) the ScanMaker 5 is 36bit
>
> WHAT BIT DEPTH?
> This leads me to another question for the 'forum':
>
> For long term digital preservation and image management what is the recommended 'colour depth' or 'bits per pixel'?
> Currently we use 8bits per pixel for our scanning (equates to 8bits greyscale and 24bits RGB) and saved as TIFF files.
> I have heard that some software programmes may have difficulty with the higher bit depth. (48bit is not recommended)
> Is there advantage in scanning to a higher bit depth then sampling back down?
>
> 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:kamorgan@UNITY.NCSU.EDU 11/07/00 04:01 >>>
> on 11/2/00 12:30 PM, Judith Terpstra at mailto:terpstja@HOTMAIL.COM wrote:
>
> > Hi
> >
> > I am new to the list, and after scanning the recent logfiles in the archives
> > I don't see any discussion of the relative merits of the current batch of
> > flatbed scanners.
>
> For our new digital media lab I purchased a Microtek Scanmaker 5 (already
> recommended here) and recently an Epson Expression 1600. I also have a Umax
> Powerlook III on my desk. All do reflective and transparency scanning and
> I'm happy with each. The Epson has a nice software interface and is
> remarkably quite. The Umax was really easy to set up, plug and play, with a
> very sophisticated interface.
>
> Keith Morgan
>
> --
> Keith Morgan - Digital Library Initiatives
> North Carolina State University Libraries
> Raleigh, NC 27695-7111 Phone: 919.515.4221
> mailto:Keith_Morgan@ncsu.edu
> http://www.lib.ncsu.edu/dli/
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