HP DesignJet Z3100ps GP 44 User Manual

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Color management
●What is color?
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The problem: color in the computer world
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The solution: color management
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Color and your printer
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A summary of the color management process
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Color calibration
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Color profiling
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Color management options
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Perform black point compensation
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Set the rendering intent
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Color emulation
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HP Professional PANTONE Emulation
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Color adjustment options
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Color management scenarios
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							What is color?
We see the world around us as steeped in color, where color is in the first instance simply an aspect of
how we experience our environment. Color is therefore subjective. Upon further inspection we find that
our color experiences are closely related to brain activity that is triggered by signals sent to it by our eyes.
These signals undergo a complex and highly interlinked sequence of processing stages that make the
relationship between what our eyes emit and what we experience anything but direct. The signals sent
by the eye depend on the light-sensitive cells that line the back of our eyes, and they belong to three types,
each sensitive to electromagnetic radiation of different physical properties (wavelengths). Such
electromagnetic radiation is called light and objects appear to have certain colors because of how they
interact with light (by emission, reflection, absorption, transmission, scattering, etc.).
Our individual experiences of color are also affected by our previous experiences and memories and by
the way in which we put our experiences into language. Finally, environmental factors such as changes
in lighting, scene content, or the proximity of other colors also have an effect, which makes the way in
which we view a given display or print an essential part of the colors we will see. Differences in all these
aspects (from physiological differences between people, to differences in their past experiences, memories
and linguistic tendencies) can result in people talking about colors differently even in response to the same
light reflected from an single object. Nonetheless there are also many similarities between how individuals
experience color and it is possible to make very specific judgments about it that others will also agree
with when care is taken in the process. In conclusion we can say that color results from the interaction
between light, objects, and a viewer, which makes it a very complex and to a large degree subjective
phenomenon.
The problem: color in the computer world
Color imaging devices such as printers, displays, projectors, and televisions create colors by different
means and by using different materials (colorants). Displays, for instance, use colorants that emit red (long
wavelength), green (medium wavelength) and blue (short wavelength) light, where outputting a white color
requires the full use of all three colorants and black requires that none of them be used (i.e. that no light
be emitted). Devices that use light emitting colorants are called additive, because the light from them is
added together before it enters a viewer’s eyes. Printers, on the other hand, use materials that absorb
parts of the light that shines on them and because of this absorption, they are called subtractive. Typical
prints use cyan (red absorbing), magenta (green absorbing) and yellow (blue absorbing) inks as well as
an additional black ink that absorbs light at all wavelengths. To get white using a printer requires not
absorbing any of the light that illuminates a piece of paper and to get black, all of the inks need to be
used to absorb all of the light that is present.
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							To control the output of color imaging devices, the following color spaces are normally used:
●RGB (Red, Green, and Blue) is the color space typically used for additive devices. A color is
represented as a combination of specific quantities of red, green, and blue colorants and all such
combinations address the range of colors (color gamut) of the chosen device.
NOTE:Subtractive devices can also be controlled using RGB data and, especially when
you do not require control over how you want to use your printer’s black ink, this is an efficient
option.
●CMYK (Cyan, Magenta, Yellow, and Black) is the color space for subtractive devices, such
as printers or presses. A color is represented as a combination of cyan, magenta, yellow, and black
(K) inks and all such combinations let you address the entire range of colors of the chosen device.
Both of these color spaces are only ways of controlling different color imaging devices and their values
do not describe colors directly. The same CMYK values, for example, will give different colors when sent
to different printers that use different inks and paper types. For example, consider a printer that can use
indoor inks or outdoor inks. The printer (hardware) is the same, but it has two different color gamuts due
to the different chemistry of the inks (dye-based versus pigmented). Furthermore, they need to work with
different paper types, as ink interaction with the paper depends on its chemistry. Thus, the colors resulting
from given CMYK values depend on the types of inks and papers that you use with a printer. If this is the
case using the same printer, you can easily imagine how different results can be obtained with printers
using different technologies and therefore using different ink chemistry.
The same happens with RGB-controlled devices. For example, imagine that two different monitors from
the same manufacturer have their white points at 9600 K and 6500 K respectively. Their colors are going
to be different because they will be related to a different white point reference. The situation is even worse
when comparing monitors from different manufacturers. As a recommendation, set the white point of your
monitor to 5000 K (also called D50), since this is the standard color temperature for the graphic arts
industries. If you dislike the appearance of D50 (you may find it too yellowish), the second choice is to
set the display to 6500 K (D65).
NOTE:The white point is the brightest neutral color that a device can reproduce or that is present
in an image. The human visual system automatically adapts to the content of an image with respect
to its white point.
Furthermore, an RGB image, such as an image obtained from a digital camera and edited on a monitor,
needs to be first converted to CMYK for a specific printer before printing. Unfortunately different devices
do not give access to the same color gamuts: there are some colors that can be shown on a display that
cannot be matched in print and vice versa. The following graphic illustrates how colors visible to the human
eye are greater than those reproduced by a typical display or printer using a specific paper type and
also how the color gamuts accessible using these two color imaging devices do not match each other.
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							1.All colors
2.Computer monitor gamut
3.CMYK press gamut
Finally, there are some color spaces that are not device-dependent, but instead represent how a viewer
sees colors, such as CIE Lab or CIECAM02 defined by the CIE (Commission Internationale de l’Éclairage).
The advantage of these spaces is that, unlike CMYK or RGB, if two objects have the same CIE Lab values
then they will look the same when viewed under the same conditions. Values in these spaces can be
obtained from measuring the light emitted or reflected by an object.
The solution: color management
There are many colors from an RGB-controlled device that can no be reproduced in a CMYK-controlled
device and vice versa. These colors are called “out-of-gamut” colors. The industry uses two steps to reduce
color differences as much as possible:
●Describe the color behavior of each device as accurately as possible
●Convert one color gamut to another as effectively as possible
The solution:
1.Describe the color behavior of a device as accurately as possible using an ICC
profile. By taking various RGB or CMYK combinations, sending them to a device, measuring the
resulting output and expressing it in a device-independent color space (e.g. CIE Lab), the color
behavior of a device can be described. The resulting relationship is stored in an ICC profile, which
is a standard file that acts as a dictionary to translate the device’s color space (CMYK or RGB) to a
device-independent color space (e.g. CIE Lab). The process of generating an ICC profile is called
profiling.
2.Convert colors as effectively as possible using a Color Management System
(CMS). A CMS is software that uses information from ICC profiles to transform one device’s color
space (defined by a source profile) into the color space of another device (defined by a destination
profile). The difficult part of the job is with those colors that exist in one device’s gamut but not in the
other. We will explore this in more detail later on.
Briefly, we can describe any CMS by the following 4 settings:
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							●CMS: CMS stands for Color Management System. It is the application that converts the color
information stored in the input image, which has the color space defined by a source profile, into
an output image that has the color space specified by a destination profile. There are many different
CMSs on the market: there are CMSs in applications, in operating systems, and in printing software
provided by printer manufacturers (in our case the HP Designjet Z3100ps GP internal RIP).
●Source profile: a description of the color behavior of the input device.
●Destination profile: a description of the color behavior of the output device.
●Rendering intent: the most difficult challenge in color management is when a color in the source
gamut does not correspond directly to a color in the destination gamut. As a perfect match is not
possible, there are different types of choices that can be made about how to treat gamut differences
and these are called rendering intent. There are four different possibilities depending on the final
output you want to achieve.
●Use Perceptual for the most pleasing final output from your original RGB image. It is suitable
for photographic content.
●Use Saturation for vivid final output. It is suitable for business graphics (charts, presentations,
etc.), but is not recommended for color matching.
●Use Relative Colorimetric for press proofing. This rendering intent provides a match for
colors that are inside both the source and destination gamuts and minimizes differences when
a match is not possible.
●Use Absolute Colorimetric for press proofing (like Relative Colorimetric), when you also
want to simulate the color of the source’s paper.
The most commonly used device color spaces and, therefore, profiles are:
●RGB mode:
●sRGB (sRGB IEC61966-2.1): for images originating typically from consumer digital
cameras and scanners and in general from the Web
●Adobe RGB (1998): for images originating typically from professional digital cameras
●Specific RGB device space: for images coming from or going to a specific RGB device that
has been profiled. The HP Designjet Z3100ps GP has the capability to measure itself and
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							generate an RGB ICC profile, describing its color behavior for the paper that was loaded at
the time of measuring.
●CMYK mode:
●SWOP: abbreviation of “Specifications for Web Offset Publications”, a set of press standards
defined for a typical US press and for different types of paper
●ISO 12647-2: a set of press standards defined by the International Standards Organization
for different types of paper (Coated, Uncoated, …)
●Other regional standards: Euroscale, JMPA, Japan Color
●Specific CMYK device space: for images coming from or going to a specific CMYK device
that has been profiled
Color and your printer
As a creative professional, predictable and dependable results from your printer are essential to getting
your job done. Predictability is a key element of an efficient color workflow. You need prints that match
your expectations with neutral grays and correct colors on your selected paper. Your prints should be
produced consistently print-to-print and printer-to-printer. Dependability ensures that every print is free of
print-quality defects and ready to use or send to your customer. You save time and effort and avoid wasting
ink and paper, and you can meet demanding production schedules by printing overnight with confidence.
HP Designjet Z3100ps GP printers have been engineered with advanced hardware and driver features
to ensure predictable and dependable results, and offer dramatic improvements in efficiency and control
for your color workflow.
HP Embedded Spectrophotometer
HP Designjet Z3100ps GP printers revolutionize professional color workflows by using a built-in
spectrophotometer for color calibration and profiling.
A spectrophotometer is a precision instrument that can determine the exact composition of light reflected
from a color patch. It splits the reflected light into different wavelength components, just as Newton’s prism
splits white light into the colors of the rainbow, and measures the strength of each component. The HP
Embedded Spectrophotometer is mounted on the printhead carriage.
The spectrophotometer allows HP Designjet Z3100ps GP printers to generate custom ICC profiles
automatically for your preferred paper types and calibrate the printers to deliver print-to-print and printer-
to-printer repeatability with less than half the color error of earlier HP Designjets, under all environmental
conditions, and even on unknown (not factory-profiled) paper types. A built-in white calibration tile,
protected by an automatic shutter, ensures reliable measurements that meet international standards.
The printer, color imaging pipeline, and professional-quality spectrophotometer with GretagMacbeth i1
color technology are integrated with the HP Color Center software for the HP Designjet Z3100ps GP.
Giving the calibration and profiling processes direct access to the writing system allows precise control
of ink levels and color separations for each printed color patch. The automated measurement process
eliminates handling the test print, provides repeatable drying times, and allows fast measurements with
precise electromechanical positioning of the spectrophotometer over the color patch. This provides
unprecedented ease of use and matches or exceeds the performance of more expensive off-line, handheld
profiling systems.
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							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.If your paper type is not already known to the printer, add it to the printers list of known papers.
See 
Add a custom paper type on page 40. Typical users may add a few custom paper types every
year.
2.Color-calibrate the paper type, for consistent colors. Calibration should be repeated every now and
then, when recommended by a printer alert (typically, every few weeks for each paper type you use).
In addition, you may wish to calibrate immediately before a particularly important print job for which
color consistency is vital.
3.Color-profile the paper type, for accurate colors. Profiling does not normally need to be repeated:
once you have a profile for a particular paper type, you can continue to use it. However, re-profiling
does no harm, and some users repeat the profiling process every month to ensure that the profile is
up to date.
4.When printing, select the correct color profile for the paper type you are using.
If you use a paper type already defined in the printer, it has a color profile already, but you should at
least calibrate it before using it.
If you define a new paper type, you are automatically led through the steps of calibration and profiling.
The following diagram shows the operations handled by the HP Color Center, in the correct order.
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							NOTE:You can perform all three operations in sequence as shown, but you can also choose to
start with or stop after any of the three operations. With one exception: color calibration is
performed automatically after adding a new paper type.
Color calibration
Color calibration enables your printer to produce consistent 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 identical prints from any two different printers situated in different
geographical locations.
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 a certain amount of printing has been done since the last calibration
●Whenever the printer has been turned off for a long period of time
●Whenever the environmental conditions (temperature and humidity) change significantly
The printer driver usually reminds you with an alert whenever you need to perform color calibration, unless
you have disabled the alerts. However, there will be no alert if the environmental conditions change.
You can check the color calibration status of the currently loaded paper at any time by pressing the View
loaded paper 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, the color calibration status of all
papers is reset to PENDING. See 
Update the firmware on page 136.
●OBSOLETE: the paper has been calibrated, but the calibration is now out of date for one of the
reasons mentioned above, and should be repeated.
●OK: the paper has been calibrated, and the calibration is up to date.
●N/A: this paper cannot be calibrated.
NOTE:Color calibration cannot be performed on plain paper, nor on any kind of
transparent material.
You can also check the color calibration status by using HP Easy Printer Care (Windows) or HP Printer
Utility (Mac OS).
You should calibrate a paper type before creating its color profile; however, you can later recalibrate
without needing to recreate the color profile.
You can start color calibration in the following ways:
●From the printer driver alert that recommends calibration.
●From the HP Color Center: select Calibrate Your Printer.
●
From the front panel: select the Image Quality Maintenance menu icon 
, then Calibrate
color.
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							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, Letter, or any larger size.
The process takes about 8–10 minutes and 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.
3.The chart is scanned and measured using the HP Embedded Spectrophotometer.
4.From the measurements made by the spectrophotometer, 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 profiling
Color calibration provides consistent colors, but consistent colors are not necessarily accurate. For
instance, if your printer prints all colors as black, its colors may be consistent but they are not accurate.
In order to print accurate colors, it is necessary to convert the color values in your files to the color values
that will produce the correct colors from your printer, your inks, and your paper. An ICC color profile is
a description of a printer, ink, and paper combination that contains all the information needed for these
color conversions.
When you have defined and calibrated a new paper type, the printer is ready to create a ICC profile for
use with your paper, which will allow you to print on it with the best possible color accuracy. Alternatively,
if your paper type is already known to the printer, you already have an appropriate ICC profile for use
with it.
Create your own profile
You can create a color profile easily by using the HP Color Center: select Create and Install ICC
Profile. The printer helps you by prompting for information about the paper, then creates and installs the
new profile automatically.
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							The process takes about 15–20 minutes and consists of the following steps.
1.A profiling chart is printed, which contains patches of each ink used in your printer. Unlike a
calibration chart, most of the patches contain combinations of more than one ink.
The printer chooses automatically between two profile charts:
●An A3 or B format for cut sheets
●A roll-paper format that minimizes paper use by printing across the full width of the roll
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.
NOTE:If you would like to use a longer drying time, you can ask the HP Color Center to
create the chart without going on to create a profile (Windows: Print target only; Mac
OS: Print ICC profiling chart). Then, later, when the chart is completely dry, you can
restart the HP Color Center and ask it to create a profile using the chart you have already
created (Windows: Create ICC profile from a target that has already been
printed; Mac OS: Scan ICC profiling chart and create ICC profile). In this case the
spectrophotometer takes a while to warm up before it is ready to scan.
3.The chart is scanned and measured using the HP Embedded Spectrophotometer.
4.From the measurements made by the spectrophotometer, the printer calculates the ICC profile for
your printer, inks, and paper type.
5.The new ICC profile is stored in the correct system folder on your computer, where your application
programs can find it.
The profile is also stored in the printer, so that other computers connected to the same printer can
copy it. HP Easy Printer Care (Windows) or HP Printer Utility (Mac OS) will notify you if your printer
has profiles that are not yet stored on your computer.
NOTE:Some applications may need to be closed and restarted in order to use a profile that has
just been created.
NOTE:You can profile a photo paper with the gloss enhancer on or off. The two profiles will be
different, so you are recommended to save them under different names.
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