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.
This article is organized into the following headings:
Preliminaries
Display and Printer Calibration
Related Topics
Preliminaries
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.
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2. Driver Installation, Enhancements and Updates
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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.
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.
Display and Printer Calibration
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4. First: Set Up Your Display
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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.
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5. Printer Calibration Introduction
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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.
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.
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7. How to Print and Compare the Test Patterns:
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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.
Printer color fidelity should now be improved.
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8. Optional: Adding Color Management
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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.
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9. Calibration with Image Processing Software
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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.
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10. Optional: Matching the Display to the Printer
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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.
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11. Handling Residual Color Errors
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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
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12. DisplayMate's Color Explore and Match
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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.
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13. Calibrating your Scanner or Digital Camera
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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.
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