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<!-- received="Tue Mar 16 07:58:32 1999 PST" -->
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<!-- sent="Tue, 16 Mar 1999 09:57:22 -0600" -->
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<!-- name="john allen pitney" -->
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<!-- email="pitney@students.uiuc.edu" -->
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<!-- subject="Re: HP Photosmart R032 problem" -->
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<!-- inreplyto="19990316163409.A3025@bitterling.LeidenUniv.nl" -->
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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>john allen pitney</b> (<a href="mailto:pitney@students.uiuc.edu"><i>pitney@students.uiuc.edu</i></a>)<br>
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<i>Tue, 16 Mar 1999 09:57:22 -0600</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#162">[ date ]</a><a href="index.html#162">[ thread ]</a><a href="subject.html#162">[ subject ]</a><a href="author.html#162">[ author ]</a>
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<li> <b>Next message:</b> <a href="0163.html">Ewald R. de Wit: "Re: HP Photosmart R032 problem"</a>
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<li> <b>Previous message:</b> <a href="0161.html">Petter Reinholdtsen: "New libtool 1.2f works fine on HP/UX 10.20"</a>
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</ul>
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<i>> > $ xscanimage [program starts, I choose /dev/scanner]</i><br>
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<i>> > Preview Window [window appears]</i><br>
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<i>> > [feed slide to PS, PS pulls in the slide a few mm]</i><br>
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<i>> > Acquire Preview [preview acquired as slide feeds *into* the PS]</i><br>
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<i>> > [preview looks okay, needs a lot of gamma correction 1.0 -> 2.2 or so]</i><br>
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<i>> > [slide is now *inside* the scanner]</i><br>
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<i>> > Scan [image is acquired as slide is pushed back *out* of the scanner]</i><br>
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<i>> > [so far, so good]</i><br>
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<i>> > Acquire Preview [again]</i><br>
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<i>> > [this time, the preview is acquired and the slide returns to its </i><br>
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<i>> > *out* position, unlike the first time]</i><br>
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<i>> > Scan [this time, the slide feeds slowly back into the scanner, then </i><br>
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<i>> > immediately reverses direction, and *then* data is acquired. Also, I </i><br>
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<i>> > believe this is where the few mm of slip occurs.]</i><br>
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<i>> </i><br>
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<i>> This is normal behaviour for this scanner, it also happens with the </i><br>
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<i>> HP windows software. Vuescan doesn't do a second pass over the slide</i><br>
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<i>> (or strip) as it scans everything at once - perhaps that's why you</i><br>
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<i>> haven't noticed this particular behaviour before. The stupidity seems</i><br>
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<i>> to be internal to the scanner.</i><br>
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<p>
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OK. I haven't noticed it, but then I don't think that I've ever caused the <br>
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HP software to reacquire a preview, since color correction shows up in its<br>
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preview window. I was re-running the Acquire Preview to see the effect <br>
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of editing the gamma curve in xscanimage. <br>
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<p>
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<i>> > Also, my test slide is a fairly typical scene, albeit without any sky </i><br>
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<i>> > showing. I find that the default straight gamma curve results in a very </i><br>
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<i>> > dark image--to fix it with gimp's levels tool, I need to set the white </i><br>
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<i>> > point to 153 (out of 255) and the gamma to about 2.50. Of course, the </i><br>
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<i>> > image gets reduced to something like 5 bits of precision after that kind </i><br>
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<i>> > of rough treatment. Does this mean the R032 is going to require a </i><br>
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<i>> > downloaded tone map just to produce a decent image?</i><br>
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<i>> </i><br>
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<i>> For dark slides, increase the Exposure Time to for example 300% and</i><br>
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<i>> apply a gamma of 2.2 if you have a PC monitor.</i><br>
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<p>
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This slide isn't particularly dark, but the image I get with a gamma of <br>
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1.0 is simply unusable. A histogram shows that it has almost no <br>
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pixels with a value above about 150 (out of 255). This is with the <br>
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recommended 150% exposure. Applying a gamma and white point correction <br>
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to the scanned image does fix it up, but, as I pointed out, it leaves <br>
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an image with very many large gaps in its histogram and markedly reduced <br>
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color resolution. <br>
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<p>
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Is it the right thing to do, to acquire an 8-bit/channel image with a <br>
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flat 1.0 gamma curve, then apply a gamma of 2.2 to the result? <br>
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<p>
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<i>> About tonemaps, I feel it is better to do this in software (on the</i><br>
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<i>> frontend side) instead of implementing it for every backend.</i><br>
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<i>> Adding some intelligence or densitometric data to the frontend will</i><br>
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<i>> benefit all scanners and not just the Photosmart.</i><br>
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<p>
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I agree there--the densitometric data should be in the frontend. My <br>
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concern is that possible the HP PS R032 can't output a usable 24-bit <br>
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image unless there is a (10x8?) tone map downloaded to it (which seems to <br>
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be happening in the VueSmart logs). <br>
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<p>
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<i>> > Last night, I tried looking at a log file produced by VueSmart. I put </i><br>
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<i>> > some up at the following URLs:</i><br>
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<i>> </i><br>
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<i>> I don't know of any interesting SCL options that this scanner could</i><br>
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<i>> still have and that's not incorporated into the newest backend</i><br>
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<i>> already. What is it that you are looking for in the vuesmart logs that</i><br>
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<i>> you like to have?</i><br>
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<p>
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I just wanted to see how VueSmart was doing such a good job! So far, I <br>
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haven't managed to get a comparable image from xscanimage/hp backend. Doing <br>
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so will require either manipulation of 10-bit data in software or <br>
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downloading a (10x8?) tone map to the scanner. <br>
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<p>
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By the way, what does the 10x8 notation mean? Map 10-bit data to 8-bit? <br>
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<p>
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Thanks for the reply! <br>
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<p>
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John<br>
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<p>
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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="0163.html">Ewald R. de Wit: "Re: HP Photosmart R032 problem"</a>
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<li> <b>Previous message:</b> <a href="0161.html">Petter Reinholdtsen: "New libtool 1.2f works fine on HP/UX 10.20"</a>
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<!-- nextthread="start" -->
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</ul>
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