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HP Designjet T1120 Printer Series - Color management

Introduction

HP Designjet T1120 printers have been engineered with advanced hardware and software features to ensure predictable and dependable results.
  • Color calibration for consistent colors.
  • One gray and two black inks provide neutral grays on all paper types.
  • The Photo Black ink provides pure blacks when printing on photo papers.
  • Color emulation of other HP Designjet printers.

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) color 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: the 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, for consistent colors. Calibration should be repeated every now and then (see Color calibrationcolorcalibrationcalibrationcolor). In addition, you may wish to calibrate immediately before a particularly important print job for which color consistency is vital.
  2. When printing, select the correct color profile for the paper type you are using.

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 similar prints from any two different printers situated in different geographical locations.
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 (temperature and humidity) change significantly
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 printer's firmware, the color calibration status of all papers is reset to PENDING.
  • OBSOLETE: the paper has been calibrated, but the 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 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 can start color calibration in the following ways:
  • From the printer 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.
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 A3 or any larger size.
The process takes about 3–5 minutes and consists of the following steps.
  1. A calibration chart is printed, which contains patches of each ink used in your printer.
    Figure : Color calibration chart
  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.
  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

These facilities are available for the HP Designjet T1120 and T1120ps printers.

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 colors 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 printer 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: 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 specify printer color management or when you send a PostScript, PDF, TIFF, or JPEG file directly to the printer through the Embedded Web Server. In either case you have to select the profiles to use as default (in case the job doesn't specify any) and the rendering intent to apply.
    • Non-PostScript (PCL, RTL, HP-GL/2): 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 previous methods, but is a little simpler and faster, and can produce good results with standard HP paper types. This kind of color management is done when you are using a non-PostScript driver and you specify printer color management, or when you send a PCL, RTL, or HP-GL/2 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 and ColorSync if you are using Mac OS.
      ColorSync is the Mac OS built-in Color Management System; so, in fact, when selecting ColorSync it is the built-in color management part of Mac OS that is performing the color management, and it is done based on the ICC profiles of specified paper type. ColorSync is available with the PCL driver only.
You are recommended to consult the Knowledge Center at http://www.hp.com/go/T1120/knowledgecenter 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 (T1120): select the Paper Type/Quality panel, then Color.
  • In the Mac OS Print dialog (T1120ps): select the Color Options panel.
  • In some applications: you can make this choice in the application.

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 different 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 HP-GL/2 or PostScript 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 (T1120): select the Paper Type/Quality panel, then Color > Printer Managed Colors > Emulated Printer.
  • In the Mac OS Print dialog (T1120ps): select the Color Options panel, then Basic > Printer Emulation.

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 print accurate colors with no need of any manual 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 subjectively pleasing rather than accurate
The printer driver provides different adjustment facilities depending on whether you are printing in color or in grayscale. If you are printing in pure black 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 Print dialog (T1120): select the Paper Type/Quality panel, then Lightness and Hue.
  • In the Mac OS Print dialog (T1120ps): 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.
Figure : Color sliders
  • The lightness slider simply makes the whole print lighter or darker.
  • The color sliders can be used to fade or emphasize 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 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 Print dialog (T1120): select the Paper Type/Quality panel, then Gray balance.
  • In the Mac OS Print dialog (T1120ps): select the Color Options panel, then Gray balance.
Under either operating system, you will then be able to make adjustments using separate controls for highlights, midtones, and shadows.
Figure : Grayscale sliders
  • The lightness slider simply makes the whole print lighter or darker. This slider is available under Windows in the same window as the other grayscale controls; it is available under Mac OS by selecting Lightness and Hue.
  • The zone definition sliders can be used to define what you mean by highlight, midtone, and shadow.
  • The other controls for highlight, midtone, and shadow 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 (T1120ps only)

This facility is available when printing on the HP Designjet T1120ps 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. But the application does not take the printer or the paper type into account, it merely produces a generic approximation of the PANTONE color, which will look different on different printers 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 Emulation, 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 printer, together with a measure of the color difference (ΔE) between each emulation and the original PANTONE spot color. So HP Professional PANTONE Emulation not only provides the closest match that 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.

Color emulation

Your printer can emulate the color behavior of other 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, and Printer Managed Colors.
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 printers will produce different colors from the same CMYK data. If the image file you are printing was not created specifically for your HP Designjet 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 default 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 produce quality separations using U.S. inks under the following printing conditions: 260% 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: 350% 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 conditions: 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.
  • 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 specification for type 3 (coated) paper. It is designed to produce quality separations using 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 separations 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 separations 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 application 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 conversion is done by the application or operating system, and therefore the data arrive 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 hardware and software manufacturers, and is becoming the default color space for many scanners, printers, and software applications.
  • ColorMatch RGB emulates the native color space of Radius Pressview monitors. This space provides a smaller gamut alternative to Adobe RGB (1998) for print production work.
  • Apple RGB emulates the characteristics of the average 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 printer using the Embedded Web Server's Submit Job page, you have the following color management options.
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.
T1120 and T1120ps options
  • 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 different HP Designjet printer. Default: Off (no printer emulation).
T1120ps options (with PostScript or PDF jobs)
  • 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 print may not be reproducible by the printer. The rendering intent allows you to select one of four different 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 probably 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 whether to adjust for differences in black points when converting colors between color spaces. When this option is selected, 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 source space is darker than that of the destination space. This option is allowed only when the Relative colorimetric rendering intent is selected (see Rendering intentrendering intent).

Printing PANTONE swatch books

You can use the Embedded Web Server to print a swatch book showing emulations of PANTONE colors as made by your printer, together with a measure of the color difference (ΔE) between each emulation and the original PANTONE spot color.
To print a swatch book, select the Embedded Web Server's Main tab, then HP Professional PANTONE Emulation. Select the PANTONE stock to emulate, then the PANTONE colors that you want to print. When you have selected all the colors you want, press the Print button.
Figure : Swatch book example

Color management from the front panel

You can color-calibrate the loaded paper type from the front panel by selecting the Image Quality Maintenance menu icon , then Calibrate color. See Color calibrationcolorcalibrationcalibrationcolor.
The other color options in the front panel can all be found by selecting the Setup menu icon , then Printing preferences > Color.
note:
These front panel settings can all be overridden by the printer driver or Embedded Web Server settings.
T1120 and T1120ps options
  • Color/Grayscale: you can choose to print in color or in shades of gray. Default: Print in color.
  • Select RGB source profile: you can choose from a selection of RGB source profiles recognized by the printer. Default: sRGB (HP).
  • Emulate printer: you can choose to emulate a different HP Designjet printer. Default: None (no printer emulation).
    note:
    If you have old HP-GL/2 or PostScript files made for a different HP Designjet printer, you can send them to the printer and use the front panel to turn on the appropriate emulation mode.
T1120ps options (with PostScript or PDF jobs)
  • Select CMYK source profile: you can choose from a selection of CMYK source profiles recognized by the printer. Default: Europe ISO Coated FOGRA27.
  • Select rendering intent: you can select the rendering intent. Default: Perceptual.
  • Black point compensation: you can turn black point compensation on or off. Default: On.
  • HP Professional PANTONE Emulation: you can turn HP Professional PANTONE Emulation on or off. Default: On.