HP Color 4500 and printing gray bars

Hello -

The PS file below surprised me when I viewed the output under a
microscope. The gray bars are actually printed from a mix of CMYK.
However, if I comment out the line that prints the cyan lines, then
the gray lines get printed using only black.

I have some questions ...
1) Can someone explain why this is? I'm guessing it is related to
halftones, but my understanding of this topic is weak.
2) Can anyone suggest a way to get the printer to print the gray using
just black, while still printing the cyan?

FWIW, I am printing the file by copying it to the network name (i.e.
copy subset.ps \\server\printer).

Thanks in advance,
Paul

------------------------------- Begin included PS file --------------
%!PS-Adobe-3.0

%612 792 /letter setpagesize

/pagesave save store % Save VM state

100 dict begin
%%EndPageSetup
gsave mark

% Simple variables for later use
/str 500 string def % Dummy string for number - string conversions

% Shorthand for setting primary colors
/cyan {1 0 0 0 setcmykcolor} def
/black {0 0 0 1 setcmykcolor} def
/black33 {0 0 0 0.33 setcmykcolor} def

% Called with one parameter - the LPI for this box
/VerRes {
50
% save state and set origin
gsave currentpoint translate
% Set scaling to inches to simplify
72 72 scale
% Set the linewidth
dup 2 mul 1 exch div setlinewidth
% loop for 1/2 inch, drawing the lines
0 exch 1 exch 2 div 1 sub {
% move to starting point for line
2 mul 0.5 add currentlinewidth mul 0 moveto
% draw and stroke a 1/2 inch line
0 0.5 rlineto stroke
} for
% restore state
grestore
} def

% Why are the black33 lines dithered in CMY - not made of black?
300 600 moveto black VerRes
340 600 moveto black33 VerRes
%380 600 moveto cyan VerRes

cleartomark end
pagesave restore % Restore VM state

showpage
-------------------------------- End included PS file ---------------

(Paul Walker) wrote:

The PS file below surprised me when I viewed the output under a
microscope. The gray bars are actually printed from a mix of CMYK.
However, if I comment out the line that prints the cyan lines, then
the gray lines get printed using only black.

I have some questions ...
1) Can someone explain why this is? I'm guessing it is related to
halftones, but my understanding of this topic is weak.

It sounds as if the printer has a system for previewing the page to
decide whether it is in colour. If it does not seem to be in colour,
the C,M,Y engines are switched off. Otherwise, it would be processed
as a colour job.

You might still expect that a CMYK value of 0,0,0,X print only using
the blank engine. If it doesn't, I would suspect that there are
colour management options in the printer, and that they are turned on.

Any form of colour management can be expected to convert all colours
to Lab and back to CMYK, with no connection to the original channel
mix.
----------------------------------------
Aandi Inston http://www.quite.com
Please support usenet! Post replies and follow-ups, don't e-mail them.

Paul Walker wrote:

Hello -

The PS file below surprised me when I viewed the output under a
microscope. The gray bars are actually printed from a mix of CMYK.
However, if I comment out the line that prints the cyan lines, then
the gray lines get printed using only black.

I have some questions ...
1) Can someone explain why this is? I'm guessing it is related to
halftones, but my understanding of this topic is weak.
2) Can anyone suggest a way to get the printer to print the gray using
just black, while still printing the cyan?

FWIW, I am printing the file by copying it to the network name (i.e.
copy subset.ps \\server\printer).

Thanks in advance,
Paul

[...]


Well, this printer supports CMYK but usually uses CMY only (probably
because conversion from RGB to CMY is easier to handle than to CMYK.
To check, insert
/ProcessColorModel /DeviceCMYKsetpagedevice
at the beginning of your PS file and check again. If that does not
change anything, additionally add
false ColorSmartColorMatching
to switch off the built-in color management.

Helge

--
Helge Blischke
Softwareentwicklung
SRZ Berlin | Firmengruppe besscom
http://www.srz.de
tel: +49 30 75301-360

Helge Blischke wrote in message ...
Paul Walker wrote:

Hello -

The PS file below surprised me when I viewed the output under a
microscope. The gray bars are actually printed from a mix of CMYK.
However, if I comment out the line that prints the cyan lines, then
the gray lines get printed using only black.

I have some questions ...
1) Can someone explain why this is? I'm guessing it is related to
halftones, but my understanding of this topic is weak.
2) Can anyone suggest a way to get the printer to print the gray using
just black, while still printing the cyan?

FWIW, I am printing the file by copying it to the network name (i.e.
copy subset.ps \\server\printer).

Thanks in advance,
Paul

[...]


Well, this printer supports CMYK but usually uses CMY only (probably
because conversion from RGB to CMY is easier to handle than to CMYK.
To check, insert
/ProcessColorModel /DeviceCMYKsetpagedevice
at the beginning of your PS file and check again. If that does not
change anything, additionally add
false ColorSmartColorMatching
to switch off the built-in color management.

Helge

The suggestions make sense. I tried them, and they don't make a
difference. I still get a mix of CMYK. I added the lines near the
beginning as follows ...
----------------- portion of file --------------
%612 792 /letter setpagesize

% HP Hacks
/ProcessColorModel /DeviceCMYK setpagedevice
%at the beginning of your PS file and check again. If that does not
%change anything, additionally add
false ColorSmartColorMatching

/pagesave save store % Save VM state
------------------ end portion ----------------

Paul

(Aandi Inston) wrote in message ...
(Paul Walker) wrote:

The PS file below surprised me when I viewed the output under a
microscope. The gray bars are actually printed from a mix of CMYK.
However, if I comment out the line that prints the cyan lines, then
the gray lines get printed using only black.

I have some questions ...
1) Can someone explain why this is? I'm guessing it is related to
halftones, but my understanding of this topic is weak.

It sounds as if the printer has a system for previewing the page to
decide whether it is in colour. If it does not seem to be in colour,
the C,M,Y engines are switched off. Otherwise, it would be processed
as a colour job.

You might still expect that a CMYK value of 0,0,0,X print only using
the blank engine. If it doesn't, I would suspect that there are
colour management options in the printer, and that they are turned on.

Any form of colour management can be expected to convert all colours
to Lab and back to CMYK, with no connection to the original channel
mix.
----------------------------------------
Aandi Inston http://www.quite.com
Please support usenet! Post replies and follow-ups, don't e-mail them.

Really strange. So far all my CMYK EPSs print CMYK exactly by numbers
(as tested by PDFs and checked by real prints).

Any form of colour management can be expected to convert all colours
to Lab and back to CMYK, with no connection to the original channel
mix.
This can happen only if the printer is in "Proof Mode" . Source color
CMYK space is converted to Lab and then to destination CMYK, as you say.
Otherwise CMYK should be applied by numbers.

It sounds as if the printer has a system for previewing the page to
decide whether it is in colour. If it does not seem to be in colour,
the C,M,Y engines are switched off. Otherwise, it would be processed
as a colour job.
I can´t believe this. A page can contain all kinds of ingredients,
and all have to be printed as they are. Such a page is he
http://www.fho-emden.de/~hoffmann/a3gencolortest.pdf

The only often observed automatism: RGB with equal values R=G=B is
printed by K-only though the source is general RGB graphic (opposed
to Grayscale).

Best regards --Gernot Hoffmann

(Gernot Hoffmann) wrote:

It sounds as if the printer has a system for previewing the page to
decide whether it is in colour. If it does not seem to be in colour,
the C,M,Y engines are switched off. Otherwise, it would be processed
as a colour job.
I can´t believe this. A page can contain all kinds of ingredients,
and all have to be printed as they are.

Printers clearly do have such a function, though. Many printers quote
different rates for black and white versus colour printing, they could
only do this if they analyse pages and print black and white in a
different way.
----------------------------------------
Aandi Inston http://www.quite.com
Please support usenet! Post replies and follow-ups, don't e-mail them.

Ed Ruf wrote:

On Sat, 23 Oct 2004 08:02:05 GMT, in comp.periphs.printers
(Aandi Inston) wrote:

Printers clearly do have such a function, though. Many printers quote
different rates for black and white versus colour printing, they could
only do this if they analyse pages and print black and white in a
different way.

Could not this also require one to say choose B&W instead of color printing
in the driver properties?

In some cases it may, but I don't think it's necessary with all
printers.
----------------------------------------
Aandi Inston http://www.quite.com
Please support usenet! Post replies and follow-ups, don't e-mail them.

Ed Ruf wrote:

Could not this also require one to say choose B&W instead of color printing
in the driver properties?

More...

It's trivially easy for the printer to discover this because it cannot
start printing until the whole page has been executed, and is stored
in some intermediate format. It has, or can easily get, bitmaps for
each plate. Checking whether three of them are blank is easy.
----------------------------------------
Aandi Inston http://www.quite.com
Please support usenet! Post replies and follow-ups, don't e-mail them.

Gernot Hoffmann schrieb:

Really strange. So far all my CMYK EPSs print CMYK exactly by numbers
(as tested by PDFs and checked by real prints).

Any form of colour management can be expected to convert all colours
to Lab and back to CMYK, with no connection to the original channel
mix.

This can happen only if the printer is in "Proof Mode" . Source color
CMYK space is converted to Lab and then to destination CMYK, as you say.
Otherwise CMYK should be applied by numbers.

Actually this is the expected behaviour, if " UseCIEColor
true setpagedevice" has been activated. In this case the PS
interpreter is supposed to remap all /DeviceXXX colors to the
color spaces described by the color space array assigned to
the /DefaultXXX /ColorSpace resources.

If the printer happens to turn on this remapping by default,
one could attempt to turn off remapping for /DeviceCMYK with

/DefaultCMYK [/DeviceCMYK] /ColorSpace defineresource pop

or even to turn off UseCIEColor completely with

/UseCIEColor false setpagedevice

(the latter of course also turns off color management for
/DeviceRGB colors in the printed PS documents)

Regards,
Gerhard

Speaking of the HP 450... Sorry to drift the discussion: I've been
told that the HP 4500 has a nasty system with a chip on the toner
cartridge(s) factory-set to allow only a limited number of prints per
cart, and that something as simple as opening and closing the
printer's cartridge-loading door, it is counted as a print count, so
if you end up opening and closing the printer several hundred times,
you end up rendering perfectly full toner carts unusable.

Can you confirm this?

Thanks
Fernando

(Paul Walker) wrote in message . com...
Hello -

The PS file below surprised me when I viewed the output under a
microscope. The gray bars are actually printed from a mix of CMYK.
However, if I comment out the line that prints the cyan lines, then
the gray lines get printed using only black.

I have some questions ...
1) Can someone explain why this is? I'm guessing it is related to
halftones, but my understanding of this topic is weak.
2) Can anyone suggest a way to get the printer to print the gray using
just black, while still printing the cyan?

FWIW, I am printing the file by copying it to the network name (i.e.
copy subset.ps \\server\printer).

Thanks in advance,
Paul

------------------------------- Begin included PS file --------------
%!PS-Adobe-3.0

%612 792 /letter setpagesize

/pagesave save store % Save VM state

100 dict begin
%%EndPageSetup
gsave mark

% Simple variables for later use
/str 500 string def % Dummy string for number - string conversions

% Shorthand for setting primary colors
/cyan {1 0 0 0 setcmykcolor} def
/black {0 0 0 1 setcmykcolor} def
/black33 {0 0 0 0.33 setcmykcolor} def

% Called with one parameter - the LPI for this box
/VerRes {
50
% save state and set origin
gsave currentpoint translate
% Set scaling to inches to simplify
72 72 scale
% Set the linewidth
dup 2 mul 1 exch div setlinewidth
% loop for 1/2 inch, drawing the lines
0 exch 1 exch 2 div 1 sub {
% move to starting point for line
2 mul 0.5 add currentlinewidth mul 0 moveto
% draw and stroke a 1/2 inch line
0 0.5 rlineto stroke
} for
% restore state
grestore
} def

% Why are the black33 lines dithered in CMY - not made of black?
300 600 moveto black VerRes
340 600 moveto black33 VerRes
%380 600 moveto cyan VerRes

cleartomark end
pagesave restore % Restore VM state

showpage
-------------------------------- End included PS file ---------------