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<TITLE>sane-devel: Re: scanning to cd-rom</TITLE>
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<META NAME="Author" CONTENT="Jonathan Buzzard (jonathan@buzzard.org.uk)">
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<META NAME="Subject" CONTENT="Re: scanning to cd-rom">
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<H1>Re: scanning to cd-rom</H1>
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<!-- received="Mon, 22 Jan 2001 00:53:35 +0000" -->
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<STRONG>From:</STRONG> Jonathan Buzzard (<A HREF="mailto:jonathan@buzzard.org.uk?Subject=Re:%20scanning%20to%20cd-rom&In-Reply-To=<E14KVEl-000627-00@happy.buzzard.org.uk>"><EM>jonathan@buzzard.org.uk</EM></A>)<BR>
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<STRONG>Date:</STRONG> Sun Jan 21 2001 - 16:53:35 PST
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<LI><STRONG>Previous message:</STRONG> <A HREF="0239.html">FJA van Zijp: "Re: please advise: Mustek 12000SP, NCR810 & color stripes"</A>
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<LI><STRONG>In reply to:</STRONG> <A HREF="0234.html">Adam Tauno Williams: "Re: scanning to cd-rom"</A>
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<LI><STRONG>Next in thread:</STRONG> <A HREF="0242.html">Steve Underwood: "Re: scanning to cd-rom"</A>
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<LI><STRONG>Reply:</STRONG> <A HREF="0242.html">Steve Underwood: "Re: scanning to cd-rom"</A>
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<A HREF="mailto:awilliam@whitemice.org?Subject=Re:%20scanning%20to%20cd-rom&In-Reply-To=<E14KVEl-000627-00@happy.buzzard.org.uk>">awilliam@whitemice.org</A> said:
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<BR>
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<EM>> At the current costs of hard drives is it unfeasible to maintain
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</EM><BR>
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<EM>> "online" archives that get backed up using ordinary means? Modern
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</EM><BR>
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<EM>> magnetic tape (something like 4mm) has a very long sheld life and is
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</EM><BR>
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<EM>> very inexpensive. If copies of online data are stored off site
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</EM><BR>
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<EM>> periodically it would seem the data is almost indesctructable.
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</EM><BR>
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<P>Have you any real experience of using 4mm magnetic tape? I would not
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<BR>
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recommend to anyone that they use DAT tapes to store anything long
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<BR>
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term.
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<BR>
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<P>That said CD-R's have when stored properly a shelf life that is much
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<BR>
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longer than needed. For best shelf life use the proper gold disks as
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<BR>
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this dye is much more stable than the silvery ones. You should get
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<BR>
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about 30 years when stored correctly. You can pay extra and get ones
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<BR>
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with longer rated shelf lives as well, something in the region of 100
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<BR>
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years I believe but this is unnecessary.
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<BR>
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<P>All that said, with any long term data storage you need to consider
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<BR>
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how you are going to read it in 10, 20 or even 50 years from now.
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<BR>
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<P>From this comes the most important aspect. Expect to migrate *all*
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<BR>
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your data to a new physical media format about every 10 years. That is
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<BR>
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long before your CD's start going off so to speak you will find that
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<BR>
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it is getting harder to find equipment to read them. Therefore you
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<BR>
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need to monitor the situation and be prepared to act in good time to
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<BR>
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move the data to new physical media before the old becomes unreadable.
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<BR>
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<P>The second aspect is the format in which you choose to store the images.
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<BR>
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I personally would recommend the use of the PGM and PPM formats (binary
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<BR>
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version not the ASCII one) and store them uncompressed in any way. The
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<BR>
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reasons for this are two fold.
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<BR>
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<P>Firstly the file format is very simple. If you drop an ASCII copy of
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<BR>
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the file format on every CD you make then in 20 years time you will
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<BR>
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always be able if necessary to write your own software to take the images
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<BR>
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and convert them to something that the software of the day can read.
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<BR>
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Consider what graphics file formats where popular 20 years ago and ask
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<BR>
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what current graphics packages can read these and you will see my point.
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<BR>
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Just the ASCII text formated output of the ppm and pgm man pages will
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<BR>
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do for the format information.
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<BR>
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<P>The reason for storing the pictures uncompressed is that should the worst
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<BR>
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come to the worst and somehow one or two bits of the data in the middle
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<BR>
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of the file go walkies then the impact on the file is negligible. If
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<BR>
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the file is compressed and you change so much as a single bit somewhere
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<BR>
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in the middle large amounts of the image become very difficult to recover.
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<BR>
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To back this up I always store and index CSV ASCII file on every CD that
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<BR>
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has a number of fields. The first is the name of the file, the second
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<BR>
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is the size of the file in pixels WxH and the third is a one line description
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<BR>
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of the image.
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<BR>
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<P>Finally I recommend that you make two copies of each CD and arrange for
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<BR>
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the second copy to be stored elsewhere. If they are family photos then
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<BR>
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I suggest a number member of the family, brother/sister etc. that lives
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<BR>
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at different address and store both sets of CD in proper media chest.
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<BR>
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<P>A last hint is that you don't need to keep the CD's in their jewel cases.
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<BR>
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You can get special archival sleeves to keep them in, in which case
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<BR>
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you can get many more CD's inside your media chest.
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<BR>
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<P>JAB.
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<BR>
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<P><PRE>
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--
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Jonathan A. Buzzard Email: <A HREF="mailto:jonathan@buzzard.org.uk?Subject=Re:%20scanning%20to%20cd-rom&In-Reply-To=<E14KVEl-000627-00@happy.buzzard.org.uk>">jonathan@buzzard.org.uk</A>
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Northumberland, United Kingdom. Tel: +44(0)1661-832195
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<P><P><P>--
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Source code, list archive, and docs: <A HREF="http://www.mostang.com/sane/">http://www.mostang.com/sane/</A>
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To unsubscribe: echo unsubscribe sane-devel | mail <A HREF="mailto:majordomo@mostang.com?Subject=Re:%20scanning%20to%20cd-rom&In-Reply-To=<E14KVEl-000627-00@happy.buzzard.org.uk>">majordomo@mostang.com</A>
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</PRE>
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<LI><STRONG>Previous message:</STRONG> <A HREF="0239.html">FJA van Zijp: "Re: please advise: Mustek 12000SP, NCR810 & color stripes"</A>
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<LI><STRONG>In reply to:</STRONG> <A HREF="0234.html">Adam Tauno Williams: "Re: scanning to cd-rom"</A>
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<LI><STRONG>Next in thread:</STRONG> <A HREF="0242.html">Steve Underwood: "Re: scanning to cd-rom"</A>
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<LI><STRONG>Reply:</STRONG> <A HREF="0242.html">Steve Underwood: "Re: scanning to cd-rom"</A>
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<EM>
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This archive was generated by <A HREF="http://www.hypermail.org/">hypermail 2b29</A>
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: <EM>Mon Jan 22 2001 - 03:10:48 PST</EM>
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