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[filmscanners] Re: Printer drivers at 720ppi

on 10/24/03 2:26 AM, Paul D. DeRocco at pderocco@ix.netcom.com wrote:

>> From: robg@wordweb.com
>> I was on the Epson list for a long time and this is the first time I've
>> heard someone make this statement about the internal behaviour of
>> the Epson
>> driver.  Can I ask where this knowledge comes from?  In the past I found
>> a formula written by Epson themselves which gave the optimal ppi
>> for photos
>> as 240ppi.
> It's easy to prove for yourself. Take this test image:
> http://www.pbase.com/image/22493977
> which consists of alternating 1-pixel black and white lines, at 720ppi, and
> print it out. It will look gray. Print it at 1440, and one half will look
> white, because it skips the black lines, and the other half will look black,
> because it skips the white lines. Print it at some odd size, like 730, and
> you'll see nasty alias bars.
>> I'm also wondering how the figure of 720 ppi you state above is unaffected
>> by the model of the printer.  The old Epson 3000 was only "720 dpi", and
>> most of the Epson printers are "720 dpi" in one direction.  But some of
>> the recent printers are "2880 dpi" in one direction.  Does the
>> magic number
>> still apply to the most recent printers?  It sounds surprising
>> that it would
>> apply to every Epson ever made.
> I've seen an official Epson document that says that its desktop printer
> drivers resample to 720ppi, and the wide format printers resample to 360ppi.
> (I don't recall the link, though.) Then, the dithering algorithm generates
> the actual dots from these pixels at whatever dot pitch the driver is set
> for.
> --
> Ciao,               Paul D. DeRocco
> Paul                mailto:pderocco@ix.netcom.com
> ------------------------------------------------------------------------------
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I printed the "Even/Odd" test print 3 times, including 360, 720, and 1440
dpi settings on the printer driver.  (On all of them, "finest detail" was
also checked.)  This was on an 1160.

I don't know what the odd and even means.

The 1440 "even" came out best, meaning that there was the smoothest gray
texture of very fine lines.  The "odd" half of that print had the appearance
of a darker line repeating once every 12 or 13 lines.

On the 720 dpi, there were darker lines irregularly spaced on both the even
and odd parts of the image, but not identically on both the even and odd

On the 360, the image width shrank to 4 cm, compared to 12.5 cm for both the
720 and 1440.  Also the height was extended from 12.5 to 16 cm.

I don't know what any of that means.  All I know is that the 1440 definitely
looks the best.

Can you shed some light on all this?


P.S.  BTW, you have some very nice art on your web site.  All the ones I saw
so far were with the 10DS.  Do you shoot film also?  How large do you print
from the 10DS?

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