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<TITLE>sane-devel: Re: Which scanners REALLY provide 36 bit output? HP?</TITLE>
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<META NAME="Author" CONTENT="Warren Young (tangent@cyberport.com)">
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<META NAME="Subject" CONTENT="Re: Which scanners REALLY provide 36 bit output? HP?">
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<H1>Re: Which scanners REALLY provide 36 bit output? HP?</H1>
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<!-- received="Sun Dec 10 19:55:59 2000" -->
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<STRONG>From:</STRONG> Warren Young (<A HREF="mailto:tangent@cyberport.com?Subject=Re:%20Which%20scanners%20REALLY%20provide%2036%20bit%20output?%20HP?&In-Reply-To=<3A34510F.11CD0212@cyberport.com>"><EM>tangent@cyberport.com</EM></A>)<BR>
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<STRONG>Date:</STRONG> Sun Dec 10 2000 - 19:59:11 PST
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<LI><STRONG>Next message:</STRONG> <A HREF="0115.html">Daniel Kerry Hiltgen: "Re: seg-faults for network access"</A>
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<LI><STRONG>Previous message:</STRONG> <A HREF="0113.html">Steffen Kluge: "Re: Which scanners REALLY provide 36 bit output? HP?"</A>
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<LI><STRONG>In reply to:</STRONG> <A HREF="0113.html">Steffen Kluge: "Re: Which scanners REALLY provide 36 bit output? HP?"</A>
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<LI><STRONG>Next in thread:</STRONG> <A HREF="0160.html">Ian Stirling: "Re: Which scanners REALLY provide 36 bit output? HP?"</A>
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<LI><STRONG>Next in thread:</STRONG> <A HREF="0059.html">Steve Underwood: "Re: Which scanners REALLY provide 36 bit output? HP?"</A>
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<P>
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Steffen Kluge wrote:
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<BR>
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<EM>>
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</EM><BR>
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<EM>> On Sat, Dec 09, 2000 at 11:00:06AM +0800, Steve Underwood wrote:
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</EM><BR>
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<EM>> > > represent all the information possible. For 19th century photography I
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</EM><BR>
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<EM>> > > believe 1200 dpi comes very close to this.
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</EM><BR>
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<EM>> >
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</EM><BR>
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<EM>> > This is about the resolution of most modern emulsions (unless you are using
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</EM><BR>
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<EM>> > super slow specialist films). I doubt the 19th centruy emulsions have
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</EM><BR>
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<EM>> > anything like that resolution. 19th century lenses are incapable of
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</EM><BR>
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<EM>> > resolving this well, anyway. Such a high resolution would only make sense
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</EM><BR>
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<EM>> > when scanning documents, or maybe paintings.
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</EM><BR>
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<EM>> >
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</EM><BR>
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<EM>> > The resolution of most film images are much poorer than most people
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</EM><BR>
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<EM>> > realise.
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</EM><BR>
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<EM>>
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</EM><BR>
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<EM>> Well, all decent 100ASA slide or negative emulsions are capable
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</EM><BR>
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<EM>> of recording in excess of 100 lines/mm, at a contrast of
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</EM><BR>
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<EM>> 1:1000. That would be 2500lpi. Good lenses can get across maybe
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</EM><BR>
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<EM>> about 1200~2000lpi. Keep in mind that the pixels in a film
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</EM><BR>
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<EM>> emulsion are scattered (and different in size), so you need a
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</EM><BR>
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<EM>> lot more pixels in an orderly rectangular grid to get the same
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</EM><BR>
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<EM>> visual resolution.
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</EM><BR>
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<P>It's worse than that. First assume a perfect photo: stable camera,
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<BR>
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perfect focus, proper exposure, no push/pull processing, etc. Given
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<BR>
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that, the maximum resolution you quote would only apply to objects
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<BR>
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exactly at the focus plane. Old photos especially have low depth of
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<BR>
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field since they couldn't afford to stop down, since the exposure time
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<BR>
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for the films and photo plates of the time was so low. Therefore, not
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<BR>
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everything in the photo is technically "in focus", and therefore will
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<BR>
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not have the best theoretical resolution.
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<BR>
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<P>Let's also not forget that these photos have doubless deteriorated.
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<BR>
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<P>1200dpi should be plenty of resolution for this work. Higher bit depths
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<BR>
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will be a plus, though, since that will capture delicate tonal
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<BR>
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gradations that will be useful when you begin fiddling with stain
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<BR>
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removal, histogram stretching, etc.
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<BR>
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<PRE>
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--
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= Warren Young -- See my Palm pages at:
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= <A HREF="http://www.cyberport.com/~tangent/palm/">http://www.cyberport.com/~tangent/palm/</A>
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=
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= ICBM Address: 36.8274040 N, 108.0204086 W, alt. 1714m
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<P>--
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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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To unsubscribe: echo unsubscribe sane-devel | mail <A HREF="mailto:majordomo@mostang.com?Subject=Re:%20Which%20scanners%20REALLY%20provide%2036%20bit%20output?%20HP?&In-Reply-To=<3A34510F.11CD0212@cyberport.com>">majordomo@mostang.com</A>
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</PRE>
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<LI><STRONG>Next message:</STRONG> <A HREF="0115.html">Daniel Kerry Hiltgen: "Re: seg-faults for network access"</A>
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<LI><STRONG>Previous message:</STRONG> <A HREF="0113.html">Steffen Kluge: "Re: Which scanners REALLY provide 36 bit output? HP?"</A>
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<LI><STRONG>In reply to:</STRONG> <A HREF="0113.html">Steffen Kluge: "Re: Which scanners REALLY provide 36 bit output? HP?"</A>
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<LI><STRONG>Next in thread:</STRONG> <A HREF="0160.html">Ian Stirling: "Re: Which scanners REALLY provide 36 bit output? HP?"</A>
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<LI><STRONG>Next in thread:</STRONG> <A HREF="0059.html">Steve Underwood: "Re: Which scanners REALLY provide 36 bit output? HP?"</A>
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