Re: Epson Photo printers - 16 bit?
Re: Epson Photo printers - 16 bit?
- Subject: Re: Epson Photo printers - 16 bit?
- From: "Ernst Dinkla" <email@hidden>
- Date: Thu, 17 Jul 2003 01:32:55 +0200
----- Original Message -----
From: "Steve Lawrence" <email@hidden>
To: "Post to ColorSync list" <>
Cc: <email@hidden>; <email@hidden>; "Andrew
Rodney" <email@hidden>
Sent: Wednesday, July 16, 2003 6:36 PM
Subject: Re: Epson Photo printers - 16 bit?
>
> Typically, users send 8-bit per channel RGB files (24-bit
>
> total) to Epson printers (2200/7600/9600). It *is* possible
>
> to send high-bit files (16-bit per channel, 48-bit total) and
>
> they print very well. The question is this: Does anyone know
>
> if the high-bit files are massaged down to 8-bit files by
>
> either the Epson printers or the Epson drivers? (or vice
>
> versa?)
>
>
Well C. David Tobie managed to give me a push before the
distraction of
>
work allowed me to complete my reply <G>.
>
>
I can't speak about the specifics of individual Epson OS
printer
>
drivers, but I can answer your question by talking about
operating
>
system (OS) level printer drivers in general.
>
>
Basically an OS printer driver receives draw commands through
the OS's
>
printer driver programming interfaces. Putting this in context
in
>
Windows, apps draw to the printer by calling OS graphics device
>
interface (GDI) application programming interface (API) calls.
The OS
>
then translates these into device driver interface (DDI) calls
which it
>
makes to the printer driver. The Mac is basically the same at a
high
>
level, except of course the Mac OS's Quickdraw graphics engine
is used.
>
It is these printer driver programming interfaces that provide
the
>
boundaries of how and what information the driver receives and
>
processes.
>
>
To return to your specific question, under Windows (3.x, 9x,
Me, NT, XP,
>
2K) the colour information for draw objects is limited to a
maximum of
>
8-bits per channel. I am almost certain that it is the same
under the
>
Mac, classic OS at least. I'll endeavour to ask one of our Mac
driver
>
engineers about OS X... or perhaps one of the Apple print team
would be
>
able to make a definitive statement. Of course this is when
printing
>
"normally". Any draw command is allowed if the OS is bypassed
and there
>
is a proprietary link between app and printer driver.
>
>
Best Wishes,
>
>
Steve Lawrence
A similar answer was given by Mike Chaney:
>
On the colorsync list the question is asked whether the Epson
>
driver itself accepts 8 or 16 bit files. Internally it will
work
>
in 16 bit (or higher) calculations somewhere like the
Gimp-print
>
driver does. I wonder whether the output to the driver of
>
PhotoShop itself isn't limited to 8 bit, printing with PS
>
Elements with the same settings delivers the same quality while
>
it is only 8 bits. Does Qimage deliver 16 bit to the driver and
>
have you any idea whether the Epson driver keeps it at that
level
>
throughout the calculations till it drops to the 8 bit level
data
>
for the printer ?
It is impossible to pass 48 bit image data (16 bits/channel) to
*any*
Windows print driver. The Windows API commands that all printing
software uses to send data to the driver are all based in 24 bit
(8
bit/channel). Since Windows itself does not provide a means to
pass
anything but 24 bit images to the driver, all software must use
the 24 bit
methods. If the Epson driver does anything in 48 bit mode, it is
doing it
after it receives the initial image in 24 bits.
Mike
>
That tells a lot. So if there are drivers that have 48 bit
input
>
they have to bypass the API side of things. I have the Wasatch
>
SoftRip too and it tries to stay away from much Windows
>
interference but I haven't found a way of 48 bit input in that
>
RIP either so there the bottleneck is at the frontside at
least.
>
Whether it actually is a bottleneck is another matter.
>
>
Wonder what Macs do in the process.
>
>
Any objection that I quote your reply in the colorsync list ?
No objection at all. As far as I know, all Windows print drivers
are
designed to accept data "the Windows way" via 24 bit "bitmaps" so
even if
you had a third party RIP that could somehow do 48 bit, it is
unlikely that
you'd be able to send data to it at 48 bit anyway unless you had
a special
plugin that knew how that particular driver supported 48 bit.
The bottom
line is that you'll never get 48 bit data to a printer using the
Windows
standard "File", "Print" command in any software because "File",
"Print"
uses the Windows standard of 24 bit.
I'm only telling you this because manufacturers could probably
figure out
a way to send 48 bit data through the normal Windows API print
driver
calls (such as sending two 24 bit images that overlay) but to do
that, you'd
have to have software that also used the same [clever] method of
getting
48 bits to the driver which still amounts to specialized printing
software to
get the job done.
Mike
End of quotes, Ernst
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