Re: Image PPI and Epson Printing
Re: Image PPI and Epson Printing
- Subject: Re: Image PPI and Epson Printing
- From: Ernst Dinkla <email@hidden>
- Date: Thu, 18 Aug 2005 22:14:46 +0200
Richard Wagner wrote:
The dealer said all
images that are to be printed with an Epson should be at a PPI
divisible into 1440/2880. If the image is at a different PPI (like
300PPI) there will be color shifts because of the conversion to a PPI
that fits into the Epson printing resolutions.
There have been arguments made that to maximize sharpness (and to
minimize interpolation error) one should send data to the printer at
the native resolution used by the printer driver so that the driver
does not need to interpolate the data up or down. Whether this results
in significantly improved image quality (or increased throughput) is
questionable, but this is likely what your rep was referring to. Your
milage may vary.
For what it's worth, from the Epson Product Support Bulletin#:
PSB.2004.03.006 (Pro96ups.pdf)
"All Epson large-format printers use 360dpi as the input resolution
(this is the resolution that data is rasterized at)..."
and
"As for the Epson desktop products, they rasterize data at 720dpi..."
This used to be significant before Photoshop broke the 30,000 pixel
barrier, as it determined the maximum page size. Photoshop CS and CS2
exceed the limitations of the Epson drivers and Photoshop is no longer
the limiting factor of maximum page size when using the Epson drivers.
--Rich Wagner
I think that bulletin isn't correct (anymore).
Qimage shows the native resolution of the printer driver based on API
information it gets from Windows. The drivers for the modern Epson
desktop models have 720 PPI mainly for all driver settings. The drivers
for the modern Epson wide formats 4000-4800-7600-9600 and I presume the
7800-9800 all have 720 PPI native resolution in the finest modes and 360
PPI below that. The Epson 10000CF driver and all Epson wide format
drivers that are older have a 360 PPI native resolution in all modes.
Qimage's up-sampling and sharpening to the native resolution takes care
of quality for most images, the anti-aliasing on down-sampling has been
improved meanwhile. The default settings work well most of the time but
less sharpening works better with very high up-sampling.
Quality of text on a 360 PPI native resolution driver/printer still can
be improved by giving it 720 PPI TIFF files that got good anti-aliasing
in the conversion from vector text. Then it is best to set Qimage's
interpolation etc off and let the driver down-sample to native
resolution with its rougher algorithm (if it actually does a down-sample
then). This is based on practice.
Qimage + the Epson driver doesn't show color differences between
different PPI files up- or down-sampled to the native resolution and
printed at a fixed printer resolution = DPI. Weird moiré and other
optical effects not counted. Different printer resolutions = DPI will
affect color consistency as you all know. Good profiles per resolution
setting should decrease that difference but not entirely. Probably due
to another gamut as the droplets have a different distribution on the paper.
Ernst
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