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<TITLE>sane-devel: Re: Which scanners REALLY provide 36 bit output? HP?</TITLE>
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<META NAME="Author" CONTENT="Steve Underwood (steveu@coppice.org)">
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<H1>Re: Which scanners REALLY provide 36 bit output? HP?</H1>
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<!-- received="Fri Dec 15 19:27:31 2000" -->
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<STRONG>From:</STRONG> Steve Underwood (<A HREF="mailto:steveu@coppice.org?Subject=Re:%20Which%20scanners%20REALLY%20provide%2036%20bit%20output?%20HP?&In-Reply-To=<3A3AE344.6D8F133C@coppice.org>"><EM>steveu@coppice.org</EM></A>)<BR>
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<STRONG>Date:</STRONG> Fri Dec 15 2000 - 19:36:36 PST
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<P>
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<LI><STRONG>Next message:</STRONG> <A HREF="0178.html">Ben Millhouse: "RE: [snapscan] Vuego 620S and ACARD scsi card"</A>
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<UL>
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<LI><STRONG>Previous message:</STRONG> <A HREF="0176.html">Oliver Rauch: "xsane-win32 as gimp plugin - work in progress."</A>
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<LI><STRONG>In reply to:</STRONG> <A HREF="0159.html">Bob Washburne: "Re: Which scanners REALLY provide 36 bit output? HP?"</A>
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<!-- nextthread="start" -->
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<LI><STRONG>Next in thread:</STRONG> <A HREF="0179.html">Marko Cebokli: "Re: Which scanners REALLY provide 36 bit output? HP?"</A>
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<LI><STRONG>Next in thread:</STRONG> <A HREF="0071.html">Steve Underwood: "Re: Which scanners REALLY provide 36 bit output? HP?"</A>
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<LI><STRONG>Reply:</STRONG> <A HREF="0179.html">Marko Cebokli: "Re: Which scanners REALLY provide 36 bit output? HP?"</A>
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<LI><STRONG>Reply:</STRONG> <A HREF="0188.html">Nick Lamb: "Waaay off topic (was Re: Which scanners REALLY provide 36 bit output? HP?)"</A>
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<HR NOSHADE><P>
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<P>
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Bob Washburne wrote:
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<BR>
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<P><EM>> > CDs can fail in as little as a year
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</EM><BR>
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<EM>> > (any make) despite the claims of 25 years for a pressed CD (which isn't that
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</EM><BR>
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<EM>> > impressive anyway) and 70-100 years for CDR (which seems completely bogus). I
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</EM><BR>
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<EM>> > live in a sauna, and things tend to fail fast, but even in dryer climates you
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</EM><BR>
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<EM>> > can never rely of any digital medium. Some years ago in the UK we stored
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</EM><BR>
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<EM>> > precious reels of data tape in a fully controlled environment to the makers
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</EM><BR>
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<EM>> > (Ampex) spec. In just two years the layers of tape had coalesced so well we
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</EM><BR>
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<EM>> > could saw through the block of tape like it was a block of wood. Of course such
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</EM><BR>
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<EM>> > extreme failure doesn't always happen. However, since you cannot tell when it
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</EM><BR>
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<EM>> > will, you cannot rely of these media. Close monitoring and recopying seems a
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</EM><BR>
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<EM>> > useless precaution, when degradation can occur so fast.
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</EM><BR>
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<EM>>
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</EM><BR>
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<EM>> So far I have not experianced the problems you have. Yes, back in the
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</EM><BR>
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<EM>> early 80's I had a large batch of nine-track tapes which went bad
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</EM><BR>
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<EM>> (Graham Magnetics). We switched to Scotch Black Watch and never had a
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</EM><BR>
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<EM>> problem since. I have yet to have a pressed CD go bad on me and the
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</EM><BR>
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<EM>> only CD-R to fail has been the dirt-cheap generic.
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</EM><BR>
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<P>The tape I referred to was Ampex. At the time it was considered the best you can
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<BR>
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get. My experience with back coated tapes is they suffer less this kind of sticking,
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<BR>
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but have other problem which don't make them much better overall. Interestingly, I
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<BR>
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have also found Scotch tapes last better than others - though those silly ads for
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<BR>
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video tape that last forever seem to be inviting trouble. As a new tape Scotch gives
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<BR>
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one of the nastiest performances, but they do score well on lengevity. They still
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<BR>
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rarely last more than 10-15 years. Many early videoed TV programs are still
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<BR>
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available in a watchable form, but then many are not. Tape can last, but don't rely
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<BR>
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on it. I live in one of the world's most humid climates (HK). Here, we buy special
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<BR>
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video tapes and floppy disks with fungicide embedded in the tape coating. Without
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<BR>
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that a stored video tape fails in no time, though they can last well if used every
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<BR>
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day.
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<BR>
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<P>I have a number of commercially pressed CDs, some less than two years old, which no
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<BR>
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drive I know of will read. They were fine the day I bought them. I have CDRs from
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<BR>
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Kodak, Mitsubishi and other top names that failed within months. Again, high
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<BR>
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humidity has no doubt aggrevated this, but I doubt it would take too long elsewhere.
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<BR>
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In the UK, which is a fairly dry climate for most of the year, I heard of quite a
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<BR>
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large number of failures in less than 10 years.
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<BR>
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<P><EM>> There are other philosophical problems to using digital media for
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</EM><BR>
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<EM>> long-term archives. Accessability. My 8" floppies may still be
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</EM><BR>
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<EM>> perfectly readable, but can *YOU* access them? You need:
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</EM><BR>
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<EM>> 1) Hardware to access the media.
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</EM><BR>
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<EM>> 2) Software to read the media
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</EM><BR>
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<EM>> 3) Software to interpret the data (JPEG, TIFF, etc.)
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</EM><BR>
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<EM>> None of which is guarenteed from decade to decade. And none of which is
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</EM><BR>
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<EM>> apparent from eye-balling the media (can you determine what the format
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</EM><BR>
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<EM>> of the data is on an unknown media?)
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</EM><BR>
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<P>I can probably find both a working 8" drive and a computer to use it with, if I look
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<BR>
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in my mother's loft. There are probably a number of collectors who could do that
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<BR>
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same. I doubt you have a disk that is still playable, though.
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<BR>
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<P><EM>> But there are great advantages as well:
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</EM><BR>
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<EM>> 1) Ease of copying.
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</EM><BR>
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<EM>> 2) No loss of signal from copy to copy. Once a pixel is digitised into
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</EM><BR>
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<EM>> a "5" that 5 remains a 5 no matter which generation copy it is. And a
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</EM><BR>
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<EM>> weak five will copy to a strong five.
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</EM><BR>
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<P>This is a weak argument in a world without perfect error correction. I have _never_
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<BR>
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seen this work out. I can make a thousand perfect copies of a disk tomorrow, but the
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<BR>
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same thing doesn't work out over time. There will always be uncorrectable errors
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<BR>
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over time, and often the media fails totally.
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<BR>
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<P><EM>> [...]
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</EM><BR>
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<EM>>
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</EM><BR>
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<EM>> 6) Reprint. As the current media, e.g. CD, becomes obsolete and a new
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</EM><BR>
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<EM>> media becomes mainline, e.g. DVD-R, copy the data onto the new media and
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</EM><BR>
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<EM>> re-publish. This is where the ECC (Error Correcting Code) format
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</EM><BR>
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<EM>> becomes important.
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</EM><BR>
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<P>ECC does nothing for a corroded, mouldy or seriously warped medium. Cohesion,
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<BR>
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adhesion, and adhesive creep don't even need warm moist conditions to screw things
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<BR>
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up 100%.
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<BR>
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<P><EM>> 7) Find a child or grandchild interested enough to carry on after me.
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</EM><BR>
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<EM>> Otherwise, the published versions in the libraries will have to suffice.
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</EM><BR>
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<P>This caring child will be looking sadly at a totally failed medium. If you keep the
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<BR>
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fragments of crumbing paper, those might still be readable.
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<BR>
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<P><EM>> At this point I will probably just keep my HP5370C unless someone
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</EM><BR>
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<EM>> responds VERY quickly that there is a much better choice out there. It
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</EM><BR>
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<EM>> has the 1200dpi, no problem. It has 14 bit A/D's and while the included
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</EM><BR>
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<EM>> software only returns a gamma corrected 8 bits, tech support swears that
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</EM><BR>
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<EM>> the hardware can return 12 bits to the computer.
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</EM><BR>
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<P>What you need is not more bits. You need a spectral shift. Your stained documents
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<BR>
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might really come alive, if you look at them through a part of the spectrum we
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<BR>
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cannot see well. You may find colours (probably in the IR band) where the stains
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<BR>
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don't show at all, and the text is beautifully clear. If you try an IR filter you
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<BR>
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might get interesting results. Most glasses will pass the high end of the IR band,
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<BR>
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and I think the CCD in the scanner will respond OK when you do a black and white
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<BR>
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scan. If you can find a suitable filter, its worth a try.
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<BR>
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<P>No amount of clever signal processing will ever reconstruct the information you have
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<BR>
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lost. A scan of a stained image at R, G and B frquencies and 128 bit resolution will
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<BR>
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have little more genuinely useful information than one stored at 8 bit resolution.
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<BR>
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The RGB scanning has already lost the most interesting stuff, since it was designed
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<BR>
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to have very similar limitations to our own eyes. Today, signal processing software
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<BR>
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exists to deblur images, destain images and perform a number of other neat tricks.
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<BR>
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Whilst its pretty amazing to see the number plate of a getaway car resolved from the
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<BR>
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blur on a very slow photo, you can't actually construct useful information out of
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<BR>
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thin air. Signal processing can only reveal what is buried in the data.
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<BR>
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<P>Regards,
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<BR>
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Steve
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<BR>
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<P><P><P><PRE>
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--
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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:%20Which%20scanners%20REALLY%20provide%2036%20bit%20output?%20HP?&In-Reply-To=<3A3AE344.6D8F133C@coppice.org>">majordomo@mostang.com</A>
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</PRE>
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<LI><STRONG>Next message:</STRONG> <A HREF="0178.html">Ben Millhouse: "RE: [snapscan] Vuego 620S and ACARD scsi card"</A>
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<LI><STRONG>Previous message:</STRONG> <A HREF="0176.html">Oliver Rauch: "xsane-win32 as gimp plugin - work in progress."</A>
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<LI><STRONG>In reply to:</STRONG> <A HREF="0159.html">Bob Washburne: "Re: Which scanners REALLY provide 36 bit output? HP?"</A>
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<!-- nextthread="start" -->
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<LI><STRONG>Next in thread:</STRONG> <A HREF="0179.html">Marko Cebokli: "Re: Which scanners REALLY provide 36 bit output? HP?"</A>
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<LI><STRONG>Next in thread:</STRONG> <A HREF="0071.html">Steve Underwood: "Re: Which scanners REALLY provide 36 bit output? HP?"</A>
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<LI><STRONG>Reply:</STRONG> <A HREF="0179.html">Marko Cebokli: "Re: Which scanners REALLY provide 36 bit output? HP?"</A>
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<LI><STRONG>Reply:</STRONG> <A HREF="0188.html">Nick Lamb: "Waaay off topic (was Re: Which scanners REALLY provide 36 bit output? HP?)"</A>
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This archive was generated by <A HREF="http://www.hypermail.org/">hypermail 2b29</A>
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