Archived posting to the Leica Users Group, 2002/09/25

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Subject: RE: [Leica] Digital Truly upon us?
From: "Austin Franklin" <darkroom@ix.netcom.com>
Date: Wed, 25 Sep 2002 23:16:12 -0400

> BD: no not trolling. Erwin Putts made me do it. blame him! :P
>
> http://www.imx.nl/photosite/leica/technics/faq.html#Anchor-Scanner-58644
>
> quote:
>
> "The result: the best 2900 scanners could capture around 35 linepairs/mm
> and the 4000 scanners managed to get slightly above 40 linepairs. But this
> value is again lost in a 300dpi digital print.
> Generally the differences between 2900 and 4000 scanners are becoming very
> small and most people would be smart to buy the much cheaper 2900 ones.
> Loss in image quality is hardly visible."

Erwin has been known to not quite have a grasp on digital technology.  The
printing resolution is entirely irrelevant to the scanner resolution, except
that you need sufficient scanned resolution to output some threshold number
of pixels (NOT DOTS) to the printer driver, like 240 PPI (Pixels Per
Inch...and that is NOT NOT NOT the same as DPI...and that's a whole
different discussion as to how Pixels get converted to Dots), or 320 PPI to
the printer, and has nothing to do with lp/mm of the original.

A 4x6 print at 300 DPI is entirely different than a 30" x 40" print at 300
DPI as far as the input image resolution requirements.  So I have no idea
what on earth he means by "this value is again lost in a 300dpi digital
print".  The printer prints at what ever resolution the printer prints at,
whether it be 360 DOTS per inch, or 720 DOTS per inch or 1440 DOTS per
inch...it's how many PIXELS per inch that you send to the printer driver
that matters, not how many dots per inch the printer prints...that's
somewhat "fixed" (like 720 or 1440 for inkjet printers, though you do have a
choice, you really want to print at what ever the highest native resolution
of the printer is for photographic images) no matter how many pixels per
inch you send to the printer driver.

Austin

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