kopia lustrzana https://gitlab.com/sane-project/website
101 wiersze
5.5 KiB
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101 wiersze
5.5 KiB
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<!-- received="Fri Mar 26 11:29:11 1999 PST" -->
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<!-- sent="Fri, 26 Mar 1999 11:28:41 -0800" -->
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<!-- name="Dean Martin Townsley" -->
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<!-- email="townsley@physics.ucsb.edu" -->
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<!-- subject="Re: Calibration problem on UMAX Astra 1220S" -->
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<!-- id="199903261928.LAA17903@spacecase.physics.ucsb.edu" -->
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<!-- inreplyto="36FB3F36.740EA8EB@wolfsburg.de" -->
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<title>sane-devel: Re: Calibration problem on UMAX Astra 1220S</title>
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<h1>Re: Calibration problem on UMAX Astra 1220S</h1>
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<b>Dean Martin Townsley</b> (<a href="mailto:townsley@physics.ucsb.edu"><i>townsley@physics.ucsb.edu</i></a>)<br>
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<i>Fri, 26 Mar 1999 11:28:41 -0800</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#239">[ date ]</a><a href="index.html#239">[ thread ]</a><a href="subject.html#239">[ subject ]</a><a href="author.html#239">[ author ]</a>
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<li> <b>Next message:</b> <a href="0240.html">Oliver Rauch: "Re: Calibration problem on UMAX Astra 1220S"</a>
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<li> <b>Previous message:</b> <a href="0238.html">Luigi Rizzo: "Re: Dexxa / Artec AS6E scanner."</a>
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</ul>
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<i>> It has nothing to do with you problem!</i><br>
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<i>> </i><br>
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<i>> What you are looking for is higlight and shadow (or black and white point)</i><br>
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<i>> definition.</i><br>
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<i>> The Astra 1220S only can do this via gamma correction, there are no seperate</i><br>
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<i>> functions</i><br>
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<i>> for this.</i><br>
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<p>
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Is it possible to make the popup help more informative on this point? Like maybe:<br>
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"Do a quality (rather than quick) internal white-calibration"<br>
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The point is to distiguish it from calibration on the image. You can decide if<br>
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this is necessary since the real problem here is that my scanner just<br>
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doesn't have a very good white point whether it's calibrated carefully or not.<br>
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Sounds like this option adresses the problem of vertical streaks more than my<br>
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problem, so maybe it should say something more along those lines, I don't know.<br>
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<p>
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<i>> Xsane makes available the highlight and shadow function via the hystogram window.</i><br>
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<i>> Open the histogram window, between the two histograms there are some colored blocks.</i><br>
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<i>> In the recent version there are three sliders in the gray block. Move the mid slider</i><br>
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<i>> and</i><br>
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<i>> the left slider to the right, as far as possible. Then do a real scan of the image.</i><br>
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<i>> On a preview</i><br>
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<i>> you will not see any differences, because the preview is always done in 24bpp, the</i><br>
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<i>> real</i><br>
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<i>> scan uses a 36bpp and afterwards converts it to a 24bpp image.</i><br>
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<i>> </i><br>
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<i>> I hope this works for you!</i><br>
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<p>
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Actually this helps a lot! Thanks for the pointer. The scan comes out actually<br>
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useful though it's still not as good as the one done on another scanner. I'm kinda<br>
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new to scanning so I don't know many tricks yet.<br>
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<p>
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<i>> > I think I could do better if I had an idea what I was looking for. What is</i><br>
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<i>> > the Quality Calibration supposed to work like? Should it happen at the</i><br>
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<i>> > beginning of each scan when the button is checked? Should the scan process</i><br>
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<i>> > be different? A two pass scan maybe? If it's not working is this because</i><br>
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<i>> > the driver is just not telling the scanner to do it properly? Is this</i><br>
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<i>> > documented anywhere or is this a trial and error type thing?</i><br>
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<i>> ></i><br>
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<i>> </i><br>
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<i>> The difference is in the short time before the real scan begins.</i><br>
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<i>> If you don`t see any differences, it is possible that the scanner</i><br>
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<i>> always does a quality calibration independent from the quality bit.</i><br>
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<i>> </i><br>
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<i>> May be you see/hear a difference between a preview scan and a</i><br>
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<i>> real scan.</i><br>
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<p>
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I see now it now. It's like a really short scan just before the actual scan. I<br>
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wasn't seeing it before because it only does it the first time you scan with it on<br>
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after a scan with it off. I was always checking in the wrong order by doing a<br>
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scan with it on (after having just done one with it on) and then one with it off.<br>
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Apparently the firmware is intelligent and doesn't redo the quality calibration if<br>
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it has just been done on the previous scan, or something like that.<br>
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<p>
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In the end I have decided the white point on this scanner is just not so good for<br>
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whetever reason. I can put in something white and something slightly off-white<br>
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and even using only the top half of the values as described above they both come<br>
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out completely white, indicating the scanner can't see the difference between<br>
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them. Oh well that's why it's not an expensive scanner I suppose (I use it mostly<br>
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for 1-bit scans of text anyhow), though I really have no way of knowing if it's<br>
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the model or just this one scanner.<br>
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<p>
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Thanks for all of your help Oliver, and thanks for your work on the software!<br>
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-Dean Townsley<br>
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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="0240.html">Oliver Rauch: "Re: Calibration problem on UMAX Astra 1220S"</a>
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<li> <b>Previous message:</b> <a href="0238.html">Luigi Rizzo: "Re: Dexxa / Artec AS6E scanner."</a>
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<!-- nextthread="start" -->
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<!-- reply="end" -->
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</ul>
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