It is funny that you should mention the 240 figure; I also remember a long
sdiscussion ont he old Leben Epson Inkjet printer list in which it was
finally concluded that the 240 ppi/dpi number was the optimum resolution to
send to the printer and any files greater than that were a waste of
processing time and storage space since the printers would reduce the
resolution down to the 240 ppi/dpi and the output would show only a
relatively small improvement over files with original resolutions of 240
ppi/dpi. It was also said that this small improvement stopped once the file
resolution sent to the printer went over 300 or 360 ppi/dpi.
I have no reason to doubt Bob or others who claim to have seen official
Epson literature on the subject which states the native printer resolution
to be 720 ppi/dpi for desktop printers and 360 ppi/dpi for wide format; but
the apparent contradiction is confusing since within the printer driver
dialog boxes you see options to set the out put resolutions at a variety of
settings - the range of options depending on the model printer - from 360,
720, 1440 to 2880. It is not very clear what the native input resolutions
for the printers are and how they relate to the output quality at the
different output resolutions.
If the printers apply a nearest neighbor interpolation on all submitted
files, including those that have true optical based resolutions of 720 ppi
or interpolated ones using better techniques, so as to reinterpolate all
incoming files using nearest neighbor before processing them for printing,
THEN it may not make any difference in output quality if the incoming file
is 240, 720, or higher. Consequently, a file with a minimum of 240 ppi,
which is a multiple of 720 ppi, may be optimum in terms of required
processing times by the printer and file sizes.
-----Original Message-----
From: filmscanners_owner@halftone.co.uk
[mailto:filmscanners_owner@halftone.co.uk]On Behalf Of robg@wordweb.com
Sent: Thursday, October 23, 2003 9:43 PM
To: laurie@advancenet.net
Subject: [filmscanners] RE: Printer drivers at 720ppi
"Bob Frost" <bobfrost@btopenworld.com> wrote:
> 240 dpi is not all that is needed, because the Epson
> driver upsamples that (or any other dpi you send it)
> to 720 dpi (desktop printers), using Nearest Neighbour
> type upsampling. So 720 dpi is what is needed by the
> driver.
Hi Bob,
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.
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.
This isn't a flame - since I have an Epson 1160 myself, I'm interested in
anything which might give better results.
Rob
PS Someone else asked about the method for scanning a whole film with the
same settings in Vuescan. I beileve you need to look at the advanced
workflow
information on Ed Hamrick's website. There is a setting in Vuescan to lock
the exposure.
-------------
How do you know if you never try?
(Rob Geraghty 25 June 2002)
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