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<!-- received="Tue Mar 16 08:23:42 1999 PST" -->
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<!-- sent="Tue, 16 Mar 1999 17:22:39 +0100" -->
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<!-- name="Ewald R. de Wit" -->
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<!-- email="ewald@pobox.com" -->
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<!-- subject="Re: HP Photosmart R032 problem" -->
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<!-- inreplyto="19990316095722.40848@ux11.cso.uiuc.edu" -->
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<title>sane-devel: Re: HP Photosmart R032 problem</title>
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<h1>Re: HP Photosmart R032 problem</h1>
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<b>Ewald R. de Wit</b> (<a href="mailto:ewald@pobox.com"><i>ewald@pobox.com</i></a>)<br>
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<i>Tue, 16 Mar 1999 17:22:39 +0100</i>
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<p>
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<ul>
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<li> <b>Messages sorted by:</b> <a href="date.html#163">[ date ]</a><a href="index.html#163">[ thread ]</a><a href="subject.html#163">[ subject ]</a><a href="author.html#163">[ author ]</a>
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<li> <b>Next message:</b> <a href="0164.html">J. Milgram: "Understanding resolution."</a>
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<li> <b>Previous message:</b> <a href="0162.html">john allen pitney: "Re: HP Photosmart R032 problem"</a>
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</ul>
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john allen pitney (<a href="mailto:pitney@students.uiuc.edu">pitney@students.uiuc.edu</a>) wrote:<br>
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<p>
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<i>> This slide isn't particularly dark, but the image I get with a gamma of </i><br>
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<i>> 1.0 is simply unusable. A histogram shows that it has almost no </i><br>
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<i>> pixels with a value above about 150 (out of 255). This is with the </i><br>
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<i>> recommended 150% exposure. Applying a gamma and white point correction </i><br>
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<i>> to the scanned image does fix it up, but, as I pointed out, it leaves </i><br>
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<i>> an image with very many large gaps in its histogram and markedly reduced </i><br>
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<i>> color resolution. </i><br>
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<p>
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150% is not by any means a recommended value (it's just the HP default<br>
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value for slides). Try a higher value and you'll get a better picture<br>
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with a somewhat smoother histogram. You mustn't set it too high<br>
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though otherwise you loose all detail in the highlights.<br>
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<br>
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<i>> Is it the right thing to do, to acquire an 8-bit/channel image with a </i><br>
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<i>> flat 1.0 gamma curve, then apply a gamma of 2.2 to the result? </i><br>
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<p>
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No it's not the right thing to do but it's the best that can be done<br>
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right now...<br>
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<p>
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<i>> I agree there--the densitometric data should be in the frontend. My </i><br>
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<i>> concern is that possible the HP PS R032 can't output a usable 24-bit </i><br>
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<i>> image unless there is a (10x8?) tone map downloaded to it (which seems to </i><br>
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<i>> be happening in the VueSmart logs). </i><br>
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<p>
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As far as I understood it Vuesmart does the tonemapping in software.<br>
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You might have mistaken the calibration data for the tonemap.<br>
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<p>
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Revision 032 of the photosmart doesn't seem to allow any tonemap up or<br>
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downloading so we will actually be forced to do it in software.<br>
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<p>
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<i>> I just wanted to see how VueSmart was doing such a good job! So far, I </i><br>
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<i>> haven't managed to get a comparable image from xscanimage/hp backend. Doing </i><br>
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<i>> so will require either manipulation of 10-bit data in software or </i><br>
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<i>> downloading a (10x8?) tone map to the scanner. </i><br>
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<p>
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Yes, the current state of affairs does suck somewhat. I'm writing a<br>
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new frontend for the KDE project that will address these and other<br>
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concerns but it will be a few months till a public release though.<br>
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<p>
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<i>> By the way, what does the 10x8 notation mean? Map 10-bit data to 8-bit? </i><br>
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<p>
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Yep!<br>
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<p>
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<pre>
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--
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-- Ewald
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<p>
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<p>
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<p>
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<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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</pre>
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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="0164.html">J. Milgram: "Understanding resolution."</a>
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<li> <b>Previous message:</b> <a href="0162.html">john allen pitney: "Re: HP Photosmart R032 problem"</a>
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<!-- nextthread="start" -->
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</ul>
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