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<TITLE>sane-devel: Re: Snapscan 310 resolution problem</TITLE>
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<META NAME="Author" CONTENT="Steve Underwood (steveu@coppice.org)">
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<META NAME="Subject" CONTENT="Re: Snapscan 310 resolution problem">
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<H1>Re: Snapscan 310 resolution problem</H1>
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<STRONG>From:</STRONG> Steve Underwood (<A HREF="mailto:steveu@coppice.org?Subject=Re:%20Snapscan%20310%20resolution%20problem&In-Reply-To=<3A25BD20.D4776AF5@coppice.org>"><EM>steveu@coppice.org</EM></A>)<BR>
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<STRONG>Date:</STRONG> Wed Nov 29 2000 - 18:36:16 PST
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<LI><STRONG>Next message:</STRONG> <A HREF="0371.html">Matt Mozur: "RH 7.0 server for Xsane Win32"</A>
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<LI><STRONG>Previous message:</STRONG> <A HREF="0369.html">Chris Pinkham: "Re: Compilation status"</A>
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<LI><STRONG>In reply to:</STRONG> <A HREF="0359.html">cbagwell@sprynet.com: "Re: Re: Snapscan 310 resolution problem"</A>
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<LI><STRONG>Maybe reply:</STRONG> <A HREF="0359.html">cbagwell@sprynet.com: "Re: Re: Snapscan 310 resolution problem"</A>
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<A HREF="mailto:cbagwell@sprynet.com?Subject=Re:%20Snapscan%20310%20resolution%20problem&In-Reply-To=<3A25BD20.D4776AF5@coppice.org>">cbagwell@sprynet.com</A> wrote:
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<BR>
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<P><EM>> This brings up a topic that was discussed a while back. Should we
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</EM><BR>
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<EM>> have a new classification for scanners that have uneven scan
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</EM><BR>
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<EM>> resolutions? Those would be allowed to interpolate so that you got
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</EM><BR>
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<EM>> an even 600 x 600 dpi. I'm assuming the vertical 600 would be a
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</EM><BR>
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<EM>> better version than pure interpolation alone could produce?
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</EM><BR>
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<P>Its hard to tell what is best. The scanner documentation I have looked at isn't
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<BR>
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too clear about what exactly the number of bits of colour depth, or the
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<BR>
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oversampled dpi figures actually mean - they like to quote big numbers for the
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<BR>
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spec., and avoid justifying them.
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<BR>
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<P>If the scanners interpolate from an oversampled analogue signal from the CCD,
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<BR>
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they could achieve substantially better oversampled resolution, in the
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<BR>
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direction of scan, than a post processing interpolator on the host could do.
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<BR>
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That is the direction which already has the natural higher resolution, though.
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<BR>
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Across the width of the scan they can interpolate before gamma correction. I
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<BR>
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think that would give a better result than interpolating on the host after
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<BR>
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gamma correction. You cannot really undo the gamma correction on the host for
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<BR>
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interpolation, as you have already lost considerable brightness resolution in
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<BR>
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the scanner's gamma corrector. Generally the 30 or 36 bits quoted on the
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<BR>
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scanner box is before gamma correction, and only 24 bits is passed back to the
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<BR>
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host..
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<BR>
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<P>So, I think a 600x1200 scanner outputting a 1200x1200 image will give a better
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<BR>
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result than interpolating to square pixels on the host. I also think that this
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<BR>
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level of interpolation is quite meaningful. I really doubt than interpolating
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<BR>
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much further has any purpose. Before I owned a scanner I thought high
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<BR>
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resolution seemed a wonderful idea. Seeing the size of scan files quickly
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<BR>
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changed my mind! The interpolated scans of 35mm film I have seen look pretty
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<BR>
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dire.
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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><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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<LI><STRONG>Next message:</STRONG> <A HREF="0371.html">Matt Mozur: "RH 7.0 server for Xsane Win32"</A>
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<LI><STRONG>In reply to:</STRONG> <A HREF="0359.html">cbagwell@sprynet.com: "Re: Re: Snapscan 310 resolution problem"</A>
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This archive was generated by <A HREF="http://www.hypermail.org/">hypermail 2b29</A>
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: <EM>Wed Nov 29 2000 - 18:14:36 PST</EM>
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