Archived posting to the Leica Users Group, 2010/06/11
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Scanned file size is indicative of the amount of information contained and
thus obtainable. At less then 10% of what a 4000 dpi scanner at 16 bit can
do from the same size negative these scans for small web images are probably
just sufficent.
For a large print from the scan I suspect not.
Greg Lorenzo
Calgary, Canada
>
> Hi all,
>
> Sorry Lluis, I don't agree with your calculations.
> A 6x6 neg. is actually 56x56 mm
> At 3200 ppi it makes 3200 x 56 / 25.4 = 7055 pixels wide
> hence the scan makes 50 MPixels (actually 49.77)
> Then the file size depends on coding. In uncompressed raw (bitmap)
> format such as .pbm, if using 8 bits per channel, it will use a memory
> space of 50 MBytes in monochrome or 150 MBytes in colour.
>
> If one scans at 1200 ppi it makes 1200 x 56 / 25.4 = 2645 pixels wide
> hence 7 MPixels.
> A 8 bit-depth .pbm monochrome file will then be 7 MBytes.
> A 8 bit - depth .pbm RGB (colour) file will be 21 MBytes.
>
> One should add the header sizes but this is negligible (.pbm headers
> use 15 bytes plus the optional comments )
>
> Some scanners may use more than 8 bits depth in order to give deeper
> dynamics.
> Once compressed it will use much less space, of course, but the
> compression ratio depends on the picture itself and on coder
> adjustments.
>
> Fins aviat,
> Jean
>
> >
> >
> > Message: 6
> > Date: Tue, 8 Jun 2010 00:51:15 +0200
> > From: Lluis Ripoll Querol <lluisripollquerol at gmail.com>
> > Subject: Re: [Leica] Film/slide scanner recommendations? Samples?
> > Anyone use Braun?
> > To: Leica Users Group <lug at leica-users.org>
> > Message-ID: <91DA40FD-337F-484D-80A5-D0342CDDD273 at gmail.com>
> > Content-Type: text/plain; charset=ISO-8859-1; format=flowed; delsp=yes
> >
> > At 3200 ppi 6863 x 683 pixels , 90 MB
> >
> > At 1200 ppi 2400 x 2400 pixels, 5,8 MB
> >
> > If you need others, let me know
> >
>
> _______________________________________________
> Leica Users Group.
> See http://leica-users.org/mailman/listinfo/lug for more information
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