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<!-- received="Fri Feb 20 00:58:48 1998 PST" -->
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<!-- sent="Fri, 20 Feb 1998 09:45:34 +0100 (MET)" -->
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<!-- name="Rogier Wolff" -->
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<!-- email="R.E.Wolff@BitWizard.nl" -->
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<!-- subject="Re: Umax Astra 6x0S - CCD distance - Do they *really* do this that way" -->
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<!-- id="199802200845.JAA01668@cave.BitWizard.nl" -->
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<!-- inreplyto="m0y5clA-0000XeC@charon.beck-sw.de" -->
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<title>sane-devel: Re: Umax Astra 6x0S - CCD distance - Do they *really* do this that way</title>
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<h1>Re: Umax Astra 6x0S - CCD distance - Do they *really* do this that way</h1>
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<b>Rogier Wolff</b> (<a href="mailto:R.E.Wolff@BitWizard.nl"><i>R.E.Wolff@BitWizard.nl</i></a>)<br>
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<i>Fri, 20 Feb 1998 09:45:34 +0100 (MET)</i>
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<p>
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<li> <b>Messages sorted by:</b> <a href="date.html#115">[ date ]</a><a href="index.html#115">[ thread ]</a><a href="subject.html#115">[ subject ]</a><a href="author.html#115">[ author ]</a>
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<li> <b>Next message:</b> <a href="0116.html">Miguel Casteleiro: "Mustek Paragon 1200 A3 PRO"</a>
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<li> <b>Previous message:</b> <a href="0114.html">Lorenzo M. Catucci: "Scanner suggestions???"</a>
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<li> <b>In reply to:</b> <a href="0111.html">becka@rz.uni-duesseldorf.de: "Re: Umax Astra 6x0S - CCD distance - Do they *really* do this that way"</a>
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<li> <b>Next in thread:</b> <a href="0118.html">Rogier Wolff: "Re: Umax Astra 6x0S - CCD distance - Do they *really* do this that way"</a>
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<li> <b>Reply:</b> <a href="0118.html">Rogier Wolff: "Re: Umax Astra 6x0S - CCD distance - Do they *really* do this that way"</a>
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<a href="mailto:becka@rz.uni-duesseldorf.de">becka@rz.uni-duesseldorf.de</a> wrote:<br>
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<i>> </i><br>
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<i>> Hi !</i><br>
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<i>> </i><br>
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<i>> > After this change, all images (except the 4 resolutions above) need to</i><br>
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<i>> > be ccd-corrected, but with a float ccd value, -1 < ccd < 1</i><br>
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<i>> > </i><br>
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<i>> > The only way I find to ccd-correct those images is to add part of the</i><br>
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<i>> > current line value for a given channel with part of the above line value</i><br>
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<i>> > for the same channel and to use this value.</i><br>
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<i>> > </i><br>
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<i>> > For example, with a float ccd of .12, I take 88% (100-12) of the current</i><br>
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<i>> > line + 12% of the above line for blue channel and 76% (100-12*2) of the</i><br>
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<i>> > current line + 24% (12*2) of the above line for the green channel. If</i><br>
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<i>> > float ccd is <0, I swap the % values. [This is for Astra 610S, for 600S,</i><br>
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<i>> > replace green with red].</i><br>
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<i>> > </i><br>
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<i>> > >From my point of view, this may lead to reduce image quality, but I</i><br>
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<i>> > can't find another way to do this.</i><br>
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<i>> </i><br>
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<i>> >From information-theory point of view this does not reduce image quality.</i><br>
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<i>> There exists an inverse transformation, so no information lost.</i><br>
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<i>> Actually I might consider doing this for the MFS12000 alternate correction</i><br>
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<i>> scheme, which now only handles full-line distances.</i><br>
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<p>
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The image quality does get reduced.<br>
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<p>
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Samples: 0 0 34 56 23 37 67 83 0 0<br>
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no-loss averaging: 0 0 17 45 39 30 52 75 41 0 0<br>
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<p>
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is blurred: I just averaged every pixel-pair together....<br>
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<p>
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Roger. <br>
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<p>
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<pre>
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--
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If it's there and you can see it, it's REAL <a href="mailto:|___R.E.Wolff@BitWizard.nl">|___R.E.Wolff@BitWizard.nl</a> |
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<p>
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<pre>
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--
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</pre>
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<!-- body="end" -->
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<p>
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<ul>
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<!-- next="start" -->
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<li> <b>Next message:</b> <a href="0116.html">Miguel Casteleiro: "Mustek Paragon 1200 A3 PRO"</a>
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<li> <b>Previous message:</b> <a href="0114.html">Lorenzo M. Catucci: "Scanner suggestions???"</a>
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<li> <b>In reply to:</b> <a href="0111.html">becka@rz.uni-duesseldorf.de: "Re: Umax Astra 6x0S - CCD distance - Do they *really* do this that way"</a>
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<!-- nextthread="start" -->
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<li> <b>Next in thread:</b> <a href="0118.html">Rogier Wolff: "Re: Umax Astra 6x0S - CCD distance - Do they *really* do this that way"</a>
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<li> <b>Reply:</b> <a href="0118.html">Rogier Wolff: "Re: Umax Astra 6x0S - CCD distance - Do they *really* do this that way"</a>
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<!-- reply="end" -->
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</ul>
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