HP Designjet T7100 User Manual

							9 Color management
●Introduction
●
How colors are represented
●
A summary of the color management process
●
Color calibration
●
Color management from printer drivers
●
Color management from printer drivers (PostScript)
●
Color management from the Embedded Web Server
●
Color management from the front panel
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							Introduction
Your printer has been engineered with advanced hardware and software features to ensure predictable
and dependable results.
● Gray, dark gray, and matte black inks provide neutral grays on all paper types
Color printers only ●Color calibration for consistent colors
● Color emulation of other HP Designjet printers
If you have a T7100 Mono printe r, you should read the sections below on color management and
color adjustment options; you can probably  ignore the other sections of this chapter.
How colors are represented
All devices that display color use a color model to represent color in  numerical terms. Most monitors
use the RGB (Red-Green-Blue) colo r model, while most printers use the CMYK (Cyan-Magenta-Yellow-
blacK) color model.
An image can be converted from one color model to  another, but in general the conversion is not
perfect. Your printer uses the RGB color model: th e same color model that is used by your monitor.
This simplifies but does not completely solve the problem of matching colors . Each device represents
colors a little differently from another device, even  if they use the same color model. However, software
can adjust the colors in an image according to the  characteristics of the particular device, using a color
profile of the device, in order to achieve correct colors.
A summary of the color management process
To get the accurate and consistent  colors that you want, you should follow these steps for each paper
type that you use.
1. Color-calibrate the paper type, fo
r consistent colors. Calibration should be repeated every now
and then (see 
Color calibration on page 94). In addition, you may wish to calibrate
immediately before a particularly important pr int job for which color consistency is vital.
2. When printing, select the correct color 
preset for the paper type you are using.
Color calibration
Color calibration enables your printer to produce cons istent colors with the particular printheads, inks
and paper type that you are using, and under your  particular environmental conditions. After color
calibration, you can expect to get similar prints fr om any two different printers situated in different
geographical locations.
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							Some paper types cannot be calibrated. For all other paper types, calibration should be done in any of
the following circumstances:
● Whenever a printhead is replaced
● Whenever a new paper type is introduced that has 
not yet been calibrated with the current set of
printheads
● Whenever the environmental conditions (tempe
rature and humidity) change significantly
You can check the color calibration status of the currently loaded paper at any time by pressing the
View information  key on the front panel. The status may be one of the following:
● PENDING: the paper has not been calibrated.
NOTE:
Whenever you update the printers firmware, th e color calibration status of all papers is
reset to PENDING.
● OBSOLETE: the paper has been calibrated, but th
e calibration is now out of date because a
printhead has been replaced, and should be repeated.
● DONE: the paper has been calibrated, and the calibration is up to date.
● DISABLED: this paper 
cannot be calibrated.
NOTE:Color calibration cannot be performed on pl ain paper, nor on any kind of transparent
material.
You can also check the color calibration status by using the HP Utility.
You can start color calibration in the following ways:
● From the HP Utility for Windows: select  Color Center > Calibrate paper , and choose the
paper to be calibrated.
● From the HP Utility for Mac OS: select  Paper Preset Management from the HP Color Center
group, choose the paper to be calibrated, press the 
 button and select  Calibrate Paper.
● From the front panel: select the Im age Quality Maintenance menu icon 
, then Calibrate
color .
The calibration process is fully automatic and can be performed unattended after you have loaded
paper of the type you wish to calibrate—which should be A4 or any larger size. The paper on the
active roll will be calibrated; you should ensure that  the roll you want to calibrate is active. To change
the active roll, select the Paper menu icon 
, then  Select active roll .
The process takes about 3–5 minutes an d consists of the following steps.
1. A calibration chart is printed, which contains
 patches of each ink used in your printer.
2.The chart is allowed to dry for a period of time 
that depends on the paper type, so that the colors
have time to stabilize.
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							3.The chart is scanned and measured.
4. From the measurements, the printer calculates the necessary correction factors to apply for
consistent color printing on that
 paper type. It also calculates the maximum amount of each ink
that can be applied to the paper.
Color management from printer drivers
Color management options
The aim of color management is to reproduce colors as  accurately as possible on all devices: so that,
when you print an image, you see very similar co lors as when you view the same image on your
monitor.
There are two basic approaches to color management for your printer:
● Application-Managed Colors : in this case your application program must convert the colors
of your image to the color space of your prin ter and paper type, using the ICC profile embedded
in the image and the ICC profile of your printer and paper type.
● Printer-Managed Colors : in this case your application program sends your image to the
printer without any color conversion , and the printer converts the colors to its own color space. The
details of this process depend on the  graphics language that you are using.
◦ PostScript (with the PostScript upgrade):  the PostScript interpreter module inside the
printer performs the color conversion using  the profiles stored in the printer and any
additional profiles sent with the PostScript job . This kind of color management is done when
you are using the PostScript driver and you sp ecify printer color management or when you
send a PostScript, PDF, TIFF or JPEG file di rectly to the printer through the Embedded Web
Server. In either case you have to select the pr ofiles to use as default (in case the job doesnt
specify any) and the rend ering intent to apply.
◦ Non-PostScript (HP-GL/2, RTL):  the color management is done using a set of stored
color tables. ICC profiles are not used. This  method is somewhat less versatile than the
alternatives, but is a little si mpler and faster, and can produce good results with standard HP
paper types. This kind of colo r management is done when you are using a non-PostScript
driver and you specify printer  color management, or when you  send an HP-GL/2 or RTL file
directly to the printer through the Embedded Web Server.
NOTE: There are only two color spaces that the  printer can convert to its own color space
using the stored color tables: Adobe RGB and  sRGB if you are using Windows, Adobe RGB
if you are using Mac OS.
You are recommended to consult the Knowledge Center (see Knowledge Center on page 178 ) to see
how to use the color management options of your particular application.
To choose between Application-Managed Colors  and Printer-Managed Colors :
● In the Windows driver dialog:  select the Color tab.
● In the Mac OS Print dialog:  select the Color Options  panel.
● In some applications:  you can make this choice in the application.
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							Printer emulation
If you want to print a particular job and to see approximately the same colors that you would get from
printing the same job on a differe nt HP Designjet printer, you can use the emulation mode provided by
your printer.
NOTE: This option is available only when printing an HP-GL/2, PostScript or PDF job. It will work
correctly only when printing on plain,  coated or heavyweight coated paper.
●
In the Windows driver dialog:  select the Color tab, then  Printer Managed Colors , then
select  Printer Emulation  from the Source Profile list. You can then select from the Emulated
Printer list.
● In the Mac OS Print dialog:  select the Color Options  panel, then select from the Printer
Emulation list.
Color adjustment options
The aim of color management is to  print accurate colors. If you perform color management correctly,
then you should be able to prin t accurate colors with no need of any manu al color adjustments.
However, manual adjustments may be  useful in the following situations:
● If your color management is not working correctly for some reason
● If you want colors that are subjecti
vely pleasing rather than accurate
The printer driver provides different adjustment facili ties depending on whether you are printing in color
or in grayscale. If you are printing in pure bl ack and white, there are no color adjustment options.
Printing in color
You can adjust the colors of your print in similar ways under Windows and Mac OS:
● In the Windows driver dialog:  select the Color tab, ensure that the  Advanced color
adjustments  box is checked, then press the  Settings button beside it.
● In the Mac OS X 10.5 or 10.6 Print dialog:  select the Color Options  panel, select Color
from the Mode list, then press the  Adjust button.
● In the Mac OS X 10.4 Print dialog:  select the Color Options  panel, then Lightness and
Hue .
Under either operating system, you will then be able  to make adjustments using a lightness slider and
three color sliders.
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							●The lightness slider simply makes the whole print lighter or darker.
● The color sliders can be used to fade or emphasiz
e each of the primary colors in the print. The
primary colors may be red, green and blue; or  cyan, magenta and yellow; depending on the
color model used in the image.
The Reset button restores each slider to its default central position.
Printing in grayscale
You can adjust the gray balance of your prin t in similar ways under Windows and Mac OS:
● In the Windows driver dialog:  select the Color tab, ensure that the  Advanced color
adjustments  box is checked, then press the  Settings button beside it.
● In the Mac OS X 10.5 and 10.6 Print dialog:  select the Color Options  panel, select
Grayscale  from the Mode list, then press the  Adjust button.
● In the Mac OS X 10.4 Print dialog:  select the Color Options  panel, then Print in
Grayscale , then the Gray balance  tab.
Under either operating system, you will then be able  to make adjustments using separate controls for
highlights, midtones and shadows.
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							●The lightness slider simply makes the whole print li
ghter or darker. This slider is available in the
same window as the other grayscale controls, exce pt under Mac OS X 10.4, where it is available
by selecting Lightness and Hue .
● The zone definition sliders can be used to de
fine what you mean by highlight, midtone and
shadow.
● The other controls for highlight, midtone and shad
ow can be used to adjust the gray balance of
highlights, midtones and shadows respectively.
The Reset button restores each control to its default setting.
Color management from printer drivers (PostScript)
This facility is available when prin ting with the PostScript driver.
HP Professional PANTONE Emulation
When you use a named PANTONE color in an image,  your application will normally send to the
printer a CMYK or RGB approximation to that color. Bu t the application does not take the printer or the
paper type into account, it merely produces a ge neric approximation of the PANTONE color, which
will look different on different pr inters and on different papers.
HP Professional PANTONE Emulation can do a much better job by taking into account the
characteristics of the printer and the paper type. The results look as similar to the original PANTONE
colors as is possible on a given printer using a  given paper type. This technology is designed to
produce emulations similar to those set  up manually by prepress professionals.
To use HP Professional PANTONE Emulat ion, all you have to do is to turn it on. In fact, it is normally on
by default.
● In the Windows PostScript driver dialog:  go to the Color tab and select HP
Professional PANTONE Emulation .
● In the Mac OS Print dialog:  go to the Color Options  panel and select  HP Professional
PANTONE Emulation .
You can also use the Embedded Web Server to print a swatch book showing emulations of PANTONE
colors as made by your prin ter, together with a measure of the color difference (ΔE) between each
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							emulation and the original PANTONE spot color. So HP Professional PANTONE Emulation not only
provides the closest match th at can be achieved on your printer; it also gives clear information on how
close the emulation is to the original spot color. See 
Printing PANTONE swatch books on page 103 .
Color emulation
Your printer can emulate the color behavior of ot her devices: RGB devices such as monitors, and
CMYK devices such as  presses and printers.
You can set color emulation in the following ways:
● In the Windows PostScript driver dialog: select the  Color tab, and  Printer Managed
Colors.
● In the Mac OS Print dialog:  select the Color Options  panel, then select  Printer from the
Color Management list.
For a good emulation, the printer needs a specification of the colors  these devices can reproduce. The
standard way of encapsulating such information is in  ICC profiles. As part of the solution, we provide
the most common standards for the different devices.
The options are as follows.
CMYK color emulation
A traditional workflow defines color in the CMYK space.  For best results, the colors must be adjusted to
the printer, because different prin ters will produce different colors from the same CMYK data. If the
image file you are printing was  not created specifically for your printer, it will require some
readjustment, which can be done using one of the following options provided with your printer.
● None (Native) : no emulation. The printer will use its de fault internal conversion from CMYK to
RGB, without following any color standard. This  does not imply that results will be bad
● U.S. Web Coated (SWOP) 2  uses specifications designed to produce quality separations
using U.S. inks under the following printing conditions: 300% total area of ink coverage, negative
plate, coated publication-grade stock.
● U.S. Web Uncoated 2  uses specifications designed to pr oduce quality separations using U.S.
inks under the following printing conditions: 26 0% total area of ink coverage, negative plate,
uncoated white offset stock.
● U.S. Sheetfed Coated 2  uses specifications designed to  produce quality separations using U.S.
inks under the following printing conditions: 35 0% total area of ink coverage, negative plate,
bright white offset stock.
● U.S. Sheetfed Uncoated 2  uses specifications designed to  produce quality separations using
U.S. inks under the following printing conditions:  260% total area of ink coverage, negative plate,
uncoated white offset stock.
● Europe ISO Coated FOGRA27  is designed to produce quality separations for standard ISO
12647 printing under the following printing cond itions: 350% total ink coverage, positive film,
coated paper.
● Euroscale Uncoated 2  uses specifications designed to  produce quality separations using
Euroscale inks under the following  printing conditions: 260% total area of ink coverage, positive
plate, uncoated white offset stock.
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							●Japan Web Coated (Ad)  uses specifications developed  by the Japan Magazine Publisher
Association for digital proofing of images in  the Japanese magazine/advertising market.
● Japan Color 2001 Coated  uses the Japan Color 2001 specif ication for type 3 (coated) paper.
It is designed to produce quality separations us ing 350% total ink coverage, positive film and
coated paper.
● Japan Color 2001 Uncoated  uses the Japan Color 2001 specification for type 4 (uncoated)
paper. It is designed to produce quality separa tions using 310% total ink coverage, positive film
and uncoated paper.
● Japan Color 2002 Newspaper  uses the Japan Color 2002 for Newspapers specification. It
is designed to produce  quality separations using 240% total ink coverage, positive film and
standard newsprint paper.
● JMPA: Japanese standard for offset press.
● Toyo  is designed to produce quality se parations for Toyo printing presses.
● DIC is designed to produce quality separations for Dainippon Ink Company printing presses.
NOTE: These options have no effect if the applicat ion is defining its own CMYK space, known as
calibrated CMYK or CIEBasedDEFG in PostScript terminology.
RGB color emulation
Your printer is provided with the following color profiles:
● None (Native) : no emulation, for use when the color co nversion is done by the application or
operating system, and therefore the data ar rive at the printer already color-managed.
● sRGB IEC61966-2.1  emulates the characteristics of the average PC monitor. This standard
space is endorsed by many hard ware and software manufacturers, and is becoming the default
color space for many scanners, pr inters and software applications.
● ColorMatch RGB  emulates the native color space of  Radius Pressview monitors. This space
provides a smaller gamut alternative to Ad obe RGB (1998) for print production work.
● Apple RGB  emulates the characteristics of the averag e Apple monitor, and is used by a variety
of desktop publishing applications. Use this space for files that you plan to display on Apple
monitors, or for working with old desktop publishing files.
● Adobe RGB (1998)  provides a fairly large gamut of RGB colors. Use this space if you need to
do print production work with a broad range of colors.
Color management from  the Embedded Web Server
Submit Job options
When you send jobs to the printe r using the Embedded Web Servers  Submit Job page, you have
the following color management options.
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							If you leave an option set to Default, the setting saved in the job will  be used. If the job contains no
setting, the front-panel setting  in the printer will be used.
● Color/Grayscale : you can choose to print in color, in  shades of gray or in pure black and
white.
● Default RGB source profile : you can choose from a selection of RGB source profiles
recognized by the printer.
● Printer emulation : you can choose to emulate a differ ent HP Designjet printer. Default: Off (no
printer emulation).
PostScript or PDF jobs only ●Default CMYK source profile : you can choose from a selection of CMYK source profiles
recognized by the printer. Default:  Europe ISO Coated FOGRA27 .
● Rendering intent : you can select the rendering intent.
● Black point compensation : you can turn black point compensation on or off.
● HP Professional PANTONE Emulation : you can turn HP Professional PANTONE Emulation
on or off.
Rendering intent
Rendering intent is one of the settings used when doing a color transformation. As you probably know,
some of the colors you want to pr int may not be reproducible by the  printer. The rendering intent allows
you to select one of four diff erent ways of handling these  so-called out-of-gamut colors.
● Saturation (graphics) : best used for presentation graphics, charts or images made up of
bright, saturated colors.
● Perceptual (images) : best used for photographs or images  in which colors blend together. It
tries to preserve the overall color appearance.
● Relative colorimetric (proofing) : best used when you want to match a particular color. This
method is mainly used for proofing. It guarantees  that, if a color can be printed accurately, it will
be printed accurately. The other methods will prob ably provide a more pleasing range of colors
but do not guarantee that any particular color will  be printed accurately. It maps the white of the
input space to the white of the paper on which you are printing.
● Absolute colorimetric (proofing) : the same as relative colorimetric, but without mapping the
white. This rendering is also used  mainly for proofing, where the goal is to simulate the output of
one printer (including its white point).
Perform black point compensation
The black point compensation option controls whet her to adjust for differences in black points when
converting colors between color spaces. When this option is select ed, the full dynamic range of the
source space is mapped into the full dynamic range of  the destination space. It can be very useful in
preserving shadows when the black point of the sour ce space is darker than that of the destination
space. This option is allowed only when the  Relative colorimetric rendering intent is selected (see
Rendering intent on page 102).
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