I would add that particularly when dealing with greyscale or colour images,
files of that size become particularly difficult to handle from a storage
and manipulation standpoint. A 600 dpi colour image can be as large as 100
mb (for a letter/A4 page) in uncompressed format -- most image editing
applications require 3 to 4 times the size of any image for system memory to
work with the image; hence 300 mb to 400 mb of RAM just for the application
(never mind the system itself).
Based on our experiences, images approximately 1000 pixels high in typical
situations provides an image that is quite readable on the web. However,
this will depend on your source material. A better rule of thumb (as opposed
to overall resolution) is to look at the resultant height of the characters
on screen.
Hope this helps.
Tim
--------
Tim Au Yeung
Manager of Digitization Initiatives
Information Resources (Press)
University of Calgary
voice: 403.220.8975
email: ytau (at) ucalgary.ca
----- Original Message -----
From: Susan Stekel <[log in to unmask]>
To: <[log in to unmask]>
Sent: Friday, January 07, 2000 9:34 AM
Subject: Re: Greetings, and question on Scanned Images
>
>
> > My question therefore is this:
> >is there a recommended level of quality for scanning this kind of image
for
> >web-site use? Would, for example, 600 dpi be of sufficient quality, or do
> >people generally aim for a higher specification?
> >
> >Apologies if my question displays my appalling ignorance...
> >cheers
> >john
>
>
> You're not ignorant at all, and certainly not in any appalling way.
> Scanning at 600 dpi has become the standard approach for most projects
such
> as yours. It'll give you good data capture of the original. When
handling
> any historical material, it's best to scan it once, and properly, to avoid
> having to re-scan (and damage) the documents. So, scan at a high
resolution
> (like 600 dpi) and scan to a non-proprietary file format, such as TIFF.
>
> The real issue is: what image are you going to put online? A 600 dpi
image
> is a huge file that will take ages to download. Also, you don't really
get
> the benefit of all that data, since most computer monitors have a fairly
> poor resolution (not above the 75-100 dpi range). Once you have the 600
dpi
> master files, you can make low-resolution derivatives from those files, in
a
> web-ready format such as JPEG, that will load much faster while still
> presenting a readable image.
>
> My comments are only the briefest of summaries on this topic -- but I
don't
> want to weigh down the list. If you'd like clarification on anything I've
> said or would like to talk further, please feel free to contact me at the
> e-mail listed below.
>
> Best wishes,
> Susan
> ***********************************************
> Susan Stekel, M.A., M.S.I.
> Library and Archives Specialist
> --------------------------------------------------------------
> Northern Micrographics Inc.
> 2004 Kramer St. P.O. Box 2287
> La Crosse, WI 54602-2287
> (608) 781-0850 ext. 137 (voice)
> (608) 781-3883 (fax)
> [log in to unmask]
>
>
>
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