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    Calibrating Your Printer with DisplayMate    
Comprehensive Long Version
Copyright © 1990-2011 by DisplayMate Technologies Corporation. All Rights Reserved.
This article, or any part thereof, may not be copied, reproduced, mirrored, distributed or incorporated
into any other work without the prior written permission of DisplayMate Technologies Corporation.

   


Comprehensive Version: This is the Long version of the Printer Calibration article. A Short and Lite Version is also available that leaves out material for advanced or motivated users.
Printing this article: If your browser is improperly printing some pages with text cutoff on the right edge then either print in Landscape mode or reduce the font size (View Menu - Text Size) and margins (File Menu - Page Setup).

Calibrating Both the Monitor and Printer:
DisplayMate was originally created to set up and tune up computer monitors and video displays for optimum image and picture quality. But DisplayMate's analytical test patterns are equally useful for setting up and calibrating printers and any other type of input or output imaging device that can be connected to a computer, such as, for example, a scanner or digital camera. This will be the subject of this article.

Recommended by many publications:
DisplayMate has been recommended by many publications for calibrating printers, however, the product documentation concentrates on display calibration and includes only an abbreviated version of this lengthy article. So, we have prepared this article to help our customers and prospective customers understand how to use DisplayMate to calibrate printers as well as scanners and digital cameras.

DisplayMate Improves Calibration Speed and Accuracy:
Calibrating the printer and monitor to one another is a pre-requisite for doing any sort of digital imaging or photography. But trying to calibrate using a photograph is virtually impossible because all of the complex colors, intensities, and textures make it difficult to comprehend exactly how each control that you tweak is affecting the image. With DisplayMate's analytical test patterns it's much easier to see what the problem areas are and how they are improved by varying each available control.

Print the DisplayMate test patterns:
The DisplayMate test patterns are used in the same way as with a monitor, only now they are also printed, photographed and/or scanned. The test patterns allow you to accurately check, adjust, compare and match the gray-scales, color-scales and color gamuts of each device.

Is There an Easy or Automatic Way?
People frequently ask if there is an easy or automatic way to calibrate the printer. The only way to do this is with expensive instruments that measure and analyze your monitor's and printer's output. Even when instruments are used, the final calibration and touch-ups must still be done by eye by visually comparing test patterns in the same way as we discuss here. In addition, instruments must still be manually calibrated at least once. So the answer is there is no easy or automatic method and any company or product claiming to do so will only give poor or erratic results!!!

Do it only once:
While the calibration procedure can be time consuming, once completed it need not be repeated unless you make changes to your imaging devices or software. Note that minor adjustments may be necessary when you change inkjet cartridges because of manufacturing tolerances.

Outline

This article is organized into the following headings:

Preliminaries

Display and Printer Calibration

Related Topics


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Preliminaries

1. Background

Getting the display and printer to produce consistent color so that what you see on the display is what you get on the printer turns out to be a surprisingly difficult process. One reason is that the eye and brain are very sensitive and discriminating to subtle differences in color and intensity. Color reproduction involves the interaction of many complex parameters, each of which must be carefully accounted for and calibrated. The technologies involved are also very different and they give rise to significant differences in reproduction:

  • The display has a much broader color gamut than the printer, so there are colors that can be displayed on your monitor that can not be accurately printed.

  • The display uses additive RGB colored light given off by phosphors or filters, whereas the printed output uses subtractive absorption of the light reflected off the paper through CMYK pigments.

  • The display has greater color saturation, dynamic range and contrast. Printed images generally appear darker and duller.

  • The texture and brightness of the paper are also important factors.

  • Printing is inherently nonlinear because of the layering and overlapping of the different inks and variations in the relative positions, sizes and profiles of the ink dots.

Since the display is used as the visual reference in composing an image that will be printed, it is essential that these two very different imaging devices be brought into accurate colorimetric agreement with one another. Similar problems arise with input devices like scanners and digital cameras. This requires a somewhat lengthly calibration procedure, which we describe below. Fortunately, once the calibration procedure is completed it need not be repeated unless you make changes to the imaging devices or imaging software. Note that minor adjustments may be necessary when you change inkjet cartridges because of manufacturing tolerances.

2. Driver Installation, Enhancements and Updates

If you are using the Printer Driver that came installed with Windows instead of the custom driver that came with your printer, then you are probably missing important advanced controls provided by the printer's manufacturer. Those additional controls should simplify and improve the printer's calibration.

So the first step is to make sure that you have installed the custom driver for your printer. To check, go to the Control Panel and select Printers. Right click on desired printer and select Properties. Look through all of the Tabs, paying particular attention to ones that say Color or Advanced. Look for controls like Ink Density, Color, Saturation, Brightness and Contrast. Details will vary with the manufacturer and model. If you haven't installed the proper driver then find the CD that came with the printer and install it. If you can't find the CD then go to the manufacturer's website and download it.

If you are especially motivated, the next step is to check for driver updates. It's very important to get the latest and most advanced drivers for all of your image devices, particularly the video board and printer.

  • Go to each manufacturer's website and search for updated drivers and documentation.

  • Check to see if there are enhanced versions of the drivers with advanced features or controls that are not available or accessible with the standard drivers. These are not necessarily beta versions but rather have additional functionality for advanced users or users with special needs.

  • Scan the manufacturer's website for information on activating "hidden" features or controls in the drivers.

  • Contact the manufacturer's Technical Support and ask for additional information.

  • Check user groups and websites for unofficial information and enhancements. Exercise caution in making use of any unofficial information or software you obtain in this way.

3. Video Mode Settings

For all imaging and photography work you need to set the video mode to 24-bit or 32-bit "True Color" in the Display Properties Dialog box. To do this right click on the desktop, select Properties and then Settings.

  • Note: 32-bit color is just 24-bit color with an 8-bit pad, generally to improve speed performance.

  • Don't use 16-bit color - it has a very coarse gray-scale (32 steps for Red and Blue and 64 steps for Green). Images will also acquire a slight Green caste because Green has twice as many steps as Red and Blue.

  • If you have a choice, it's better to use a CRT monitor rather than an LCD, plasma or other display technology. CRTs provide the best overall color rendition because of their excellent color saturation, logarithmically linear Transfer Characteristic or Gamma, which affects the intensity reproduction in the middle intensities or midtones, and most importantly, their colors as well. The Transfer Characteristic for LCDs and other display technologies are generally less favorable.

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Display and Printer Calibration

4. First: Set Up Your Display

The first step is to properly calibrate your display because it's your working visual reference. Initially, this needs to be done independently of the printer.

  • Set up your display for optimum image and picture quality using DisplayMate.

  • Step through each DisplayMate test pattern and follow the on-screen instructions that explain what to look for in the image and what adjustments to make.

  • Be sure to use All of the display and video board controls available on your system. Carefully read your display and video board documentation for information on accessing and adjusting each of the controls.

  • If your video board includes a "Gamma" control, set it to 1.0 (linear) so that it is not affecting the image at this stage. Note: this leaves the display's own internal Gamma in effect.

  • Set the Color Temperature of the display to 6500° Kelvin, which is Daylight White. Color Temperatures of 3000° to 5000° are used in many photographic and graphics arts applications, but start out with 6500°, which is the standard for video. Note: most displays come from the factory set for 9300° Kelvin, which produces a brighter but bluer image.

  • Be sure to record all the initial and final settings so you can recall and restore them later.

5. Printer Calibration Introduction

Colors are processed through a series of software layers on the way to being printed. These include the printer driver, color management software (if any), and your image processing program (such as Adobe PhotoShop). The best way to proceed is to systematically turn on one layer at a time so that you're sure that each layer is improving rather than degrading the image.

If you use a Service Bureau to produce film or slide output instead of paper output, then transmit the same set of DisplayMate test patterns to them and proceed in the same way, although you will have to wait a day or more for the film to arrive in order to continue with the calibration.

6. Printer Driver Set Up

The first step is to set up your printer without introducing any effects from your color management or image processing software (such as Adobe Photoshop). We will bypass them now and then introduce them one-at-a-time later on.

Set all the of printer and printer driver controls to their "factory defaults" and turn off any Color Management profiles or software. This is generally done through Printer Properties. Examine each of the Tabs for the appropriate controls settings. To begin the calibration process follow the instructions in step 7 using the available controls in the Printer Driver.

7. How to Print and Compare the Test Patterns:

For this step we recommend that you use the Microsoft Paint program, which is included in all versions of Windows. This is a very simple program and we want to make sure that the test pattern images are not altered or processed in any way.

  • First, reduce the screen resolution in order to reduce the size of the printed test patterns. Also start off by using inexpensive copy paper and print at draft speed. This will cut down on ink usage and speed things up. As you get closer to a satisfactory calibration upgrade the paper, image size and print quality.

  • You are going to print selected DisplayMate test pattern images and then compare them to the monitor: You can use a wide selection of DisplayMate test patterns, but the following patterns will be useful for most users and applications: Color Scales, Color Triangle, Color Spectrum, Color Blend, Pastel Blend, Standard Colors, Extreme Gray-Scale, and 16 Intensity Levels.

    • To print a DisplayMate Test Pattern, bring up the desired pattern on-screen.

    • Press the "Print Screen" button on the keyboard. This copies the image to the Windows Clipboard.

    • Open the Microsoft Paint program in the Accessories Program Folder. This program will print or save the images to a file without modifying them.

    • Click the "Edit" menu and then "Paste." Next click the "File" menu and then "Print."

    • Also save the test pattern images to disk for use in later steps, below. Note: these test patterns are copyrighted and may only be used together with a licensed copy of DisplayMate.

    • Click the "File" menu and then "Save As." Select "24-bit Bitmap" for the file type and enter a descriptive File name for each test pattern.

  • Compare the printed test patterns to the patterns on your monitor. These analytical test patterns will make it easier to spot printer calibration errors. Examine the color and gray-scale sequences and look for problem colors and intensities.

  • Adjust each of the available controls, settings and options to improve the fidelity of the printed output. These will vary from system to system and will also vary for each stage of the calibration.

    For example, if the image is too dark and you have a Density or Contrast control then try turning it down. If you have a Brightness control try turning it up. If the image has a color cast to it and you have CMYK controls try adjusting them.

  • This is an iterative process, particularly when there are multiple adjustments that interact. Document the print settings you've used on each printed output page.

  • Repeat the above procedure until no further improvements are possible.

  • Be sure to record all of the settings so you can recall and restore them later.
Printer color fidelity should now be improved.

8. Optional: Adding Color Management

An advanced color management system is, in principle, the Holy Grail for accurate color reproduction among imaging devices such as displays, printers, scanners, cameras, etc. It is supposed to accurately transform and map all of the colors so they automatically appear the same on all the imaging devices in your system. Because printing, in particular, is a non-linear process the accuracy will depend on the sophistication of the color management algorithms and how well they were calibrated by the manufacturer. The best of these systems are very complex and expensive.

In practice, many color management implementations do not work particularly well and may even degrade rather than improve color accuracy. Not all systems include Color Management. If yours does then we will figure out in this step whether you should leave it on or turn it off.

The color management software should have built-in accurate calibration profiles for each of your image devices, and include variations for each type of paper that you will be using. Note that manufacturing tolerances make each individual printer, inkjet cartridge, scanner/camera sensor, batch of paper, etc., a little bit different, so manual adjustments and fine-tuning are still always necessary. You'll need to use the DisplayMate test patterns in the same way as in step 6.

Windows'95/98/Me/XP include basic color management support called Image Color Matching (ICM) that is designed to be used by all imaging devices. A manufacturer may include a calibrated profile that is supposed to accurately represent the colorimetric capabilities of their device. Of course, not all manufacturers and models support ICM. Some imaging devices may include their own proprietary color management capabilities that work alongside ICM. There are applications, such as Adobe Photoshop, that may include their own internal color management capabilities, which supplement ICM functionality. Finally, there are stand-alone color management applications that do their own calibrations and transformations.

If properly calibrated and implemented, color management will minimize color errors, providing WYSIWYG for your printed output. Because printers have a restricted color gamut it should also translate unprintable colors into the closest printable matches for your printer. As pointed out previously, the color matching won't be perfect because of fundamental differences between the different imaging technologies and also manufacturing tolerances. If the color management implementation on your system isn't particularly good, you may experience mixed or even negative results.

The next step is to turn on color management and see if it improves the color fidelity of the printed output we obtained without it in step 6, above. If you have icm (image color matching) profile files or advanced color management software, then activate these now and follow the How to Print and Compare Test Patterns in step 7 above, using the saved test pattern image files.

If you're using icm profiles you should find them under a Color Management Tab in Printer Properties. You may need to select among various icm profiles or perform calibrations and adjust controls in your color management software. Again, this is an iterative process. Be sure you have the latest icm profiles for your devices. When you're done the printer's color fidelity should be further improved. If not, update, delete or replace the color management profiles and software.

9. Calibration with Image Processing Software

If your Printer Driver and Optional Color Management haven't provided the desired color accuracy then you'll need to take advantage of the controls available in an image processing program. Adobe Photoshop is the most comprehensive and powerful of these, but even inexpensive programs generally provide many sophisticated adjustment tools to calibrate, correct and manipulate color hue, saturation and balance and brightness contrast, gray-scale, Gamma, etc. Some calibration tools will apply to the monitor and others to the printer.

  • First set all of the program's controls to their neutral factory defaults so that the program will not alter the input image in any way.

  • If you made any adjustments in the previous steps 6 to 8 then print one or more DisplayMate test patterns and verify that they are identical to the print samples obtained previously. This confirms that all of the image processing program controls are initially off or neutral.

  • Following the instructions in step 7, print and compare the test patterns using the saved image files. Adjust each of the available calibration controls in the image processing program to further improve the accuracy. Again, this is an iterative process. Repeat the procedure until no further improvements are possible.

  • Be sure to record all the settings so you can recall and restore them later.
Printer color fidelity should now be further improved.

10. Optional: Matching the Display to the Printer

We've now calibrated the printer as far as we can. The next step is to reverse the calibration procedure and readjust (actually misadjust) the monitor so that it looks as close as possible to the final calibrated printer output. Compare the printed DisplayMate test patterns to those on the display.

  • Adjust the display Brightness Control to match the dark-end (shadows) of the intensity scale.

  • Adjust the display Contrast Control to match the bright-end (highlights) of the intensity scale. In most cases decreasing the display Contrast will improve the match.

  • Adjust the video board Gamma control (if available - see Advanced Settings of Display Properties) to match the middle (midtones) of the intensity scale. This will also affect the midtone colors as well. Note: this control is particularly important for a good color and intensity scale match.

  • Adjust the display Color Temperature control to give the best match for the color of white and the best overall color tone and balance.

  • If your display includes RGB Drive or RGB Gain controls then further refine the Color Temperature adjustment for the best overall color tone and balance.

  • Be sure to record all the settings so you can recall and restore them later.

11. Handling Residual Color Errors

By this point you hopefully have a reasonably good match between your display and printer, but as pointed out previously, the color match won't be perfect because of fundamental differences between the different imaging technologies.

The final step in the printer color calibration process requires that you recognize what the residual color errors are and then take them into account when adjusting the image on-screen. Again, the analytical DisplayMate test patterns will make it easier to identify and classify the problem color regions so that you can mentally and visually correct for them on-screen. This will be the case whether you have a basic hobbyist system or a state of the art professional one. The tolerances will be different but the procedures the same. You can use DisplayMate's Color Explore and Match screen to analyze and quantify the color errors. See step 12, below.


--------------------
Related Topics

12. DisplayMate's Color Explore and Match

DisplayMate's Color Explore and Match screen lets you experiment and play with the full range of colors available on your system using 4 different color models: RGB, HSB, HSL, and CMYK. Three independent color panels are provided for color and intensity analysis. Match color coordinates for samples held up to the screen or print the panels for color calibration. You can also use the panels to analyze and quantify the color errors that creep into your printed output. Switch between color models at any time in order to express the colors in the most convenient coordinates.

13. Calibrating your Scanner or Digital Camera

If you have input imaging devices like a scanner or digital camera, they also require calibration. To accomplish that you will need to use the printed DisplayMate test patterns that were produced above. If you have used a Service Bureau to produce film or slide output then use them instead of the printed patterns.

Take the final set of calibrated printed DisplayMate test patterns in step 9 and scan them or photograph them with your digital camera. With the digital camera you can also photograph the display screen directly (on CRT monitors use the highest display resolution possible in order to minimize Moiré interference between the camera and monitor pixels). Print these images and compare them with the original printed patterns, or compare them directly on-screen. Any differences are due to the scanner or camera.

  • First adjust each of the available controls in Driver for the device provided by the manufacturer in order to improve the accuracy of the scanner or camera output. Again this is an iterative process.

  • Since the display is calibrated to the printer output you can use the image on the display as an image reference.

  • Repeat steps 8 and 9 above and adjust each of the available controls in order to improve color and intensity accuracy.

  • Be sure to record all the settings so you can recall and restore them later.


Comprehensive Version: This is the Long version of the Printer Calibration article. A Short and Lite Version is also available that leaves out material for advanced or motivated users.

Printing this article: If your browser is improperly printing some pages with text cutoff on the right edge then either print in Landscape mode or reduce the font size (View Menu - Text Size) and margins (File Menu - Page Setup).

Copyright © 1990-2011 by DisplayMate Technologies Corporation. All Rights Reserved.
This article, or any part thereof, may not be copied, reproduced, mirrored, distributed or incorporated
into any other work without the prior written permission of DisplayMate Technologies Corporation.

                                                                                                                                                                                                                                                                                                                   
--------------------
Copyright © 1990-2014 by DisplayMate® Technologies Corporation. All Rights Reserved.
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