Calibrate Your Monitor To Control Color In Your Photographs
BY Michael Guncheon
It was so simple
back then. The crayon box only had 16 colors. (Monica Devereux’s
had 64, but I’ve gotten over that by now…well, maybe.)
When you picked up the blue-violet crayon, it was blue-violet.
If you went over to a friend’s house and used their crayons,
it was the same blue-violet. You didn’t have to worry about
color management with crayons.
It’s not so simple now. There isn’t just one major
manufacturer of display devices like there was with crayons.
Nor are displays all made with the same ingredients like the
paraffin and pigment combinations of crayons. CRT displays use
an electron gun beaming electrons at phosphors, and LCDs use
liquid crystals to block or pass photons (light). Add to this
equation the fact that printers use an entirely different system
of producing colors, and you see how the world has changed since
Binney & Smith started making crayons.
Managing
The Monitor
Managing the appearance of your images begins with your display.
Proper calibration of your display leads to more consistent
and predictable printing results. Thankfully, tools to calibrate
your display have become more affordable and simpler to use.
You don’t have to be a color scientist to use them!
Monitor calibrators use both hardware and software. The hardware,
called a colorimeter, measures the output of your display. The
software is an application that takes control of your display
in order to create test patterns that the colorimeter can measure.
Colorimeter manufacturers include ColorVision, Digital Light
& Color, Monaco Systems and GretagMacbeth.
Offering a calibration alternative, DisplayMate utilizes a slideshow
consisting of specialized patterns. Each pattern is displayed
on your monitor along with screen instructions for achieving
calibration.
The calibration process is fairly straightforward. After installing
the software, you attach the colorimeter to your CRT or LCD
monitor. It’s important that the sensor measures just the
light coming from the display and not any ambient light in the
room, so a good contact between the sensor and the screen is
essential. Suction cups are used for CRTs, but they might damage
an LCD, so a different adapter is used. The sensor attaches
to your computer via a USB port.
Next, make sure there are no third-party programs controlling
your display card. Check the startup folder for any shortcuts
that might be running on your computer (an example of such a
program is Adobe Gamma Loader). You also should reset your monitor’s
controls to its factory settings. If you’re using a CRT,
it’s a good idea to let your monitor warm up for a half
hour to an hour if you can wait.
Basic Steps
After attaching the probe and starting the software, you need
to tell the software whether you’re calibrating an LCD
or CRT. This is because the display characteristics vary greatly
between the two.
Next, select the target white point you want to achieve. This
setting is measured in degrees Kelvin (K) and represents the
color temperature that white will be on your display. For example,
if 6,500 K is your white point, this is similar to a daylight
balance. The white you see on your display will look similar
to the white of standard print paper when viewed under normal
daylight. If you go down to 5,500 K, whites will look a little
warmer; if you go up to 9,300 K, they will look bluer. (Not
all software gives you that range, however.)
The next standard you have to choose is the gamma. Without turning
this article into a full discourse on gam-ma correction in display
devices (and thus squeezing out room for that ever-popular PCPhoto
HelpLine column), let’s just say that gamma correction
compensates for the non-linearity of displays. Your choices
might be anywhere from 2.2 to 1.0, depending on the software.
A setting of 2.2 is typical on a Windows machine and 1.8 on
a Mac.
Calibrating The Monitor
The first step the software completes is calibrating the sensor.
This may be done with the probe on the display, or you may have
to temporarily remove the probe and put it in a special calibration
holder. You also may be asked to adjust the brightness and contrast
controls of your display.
After the probe is calibrated, the calibration of the display
begins. Sit back and watch as the software begins to show a
series of test screens in the window displayed under the probe.
These test squares may consist of full whites, full blacks,
grays, and red, green and blue primaries. As each screen is
displayed, the colorimeter reads the screen and gives feedback
to the software to tell the display card how the monitor is
performing. The process of sampling all of the test screens
can take about five minutes.
After the display has been evaluated, the software transforms
the measurements into a set of color lookup tables that are
loaded into your display card. Your display is now calibrated!
DisplayMate and Adobe Gamma offer a software-only calibration
system. It works by presenting a series of test screens along
with on-screen instructions for calibrating your monitor.
Important Tips
There are a few points you should remember about calibrating
your display.
• Displays can (and do) drift over time. Although the frequency
with which you’ll calibrate your monitor varies with usage,
a monitor should be calibrated every two to four weeks for optimal
accuracy. Some software allows you to set up a reminder of when
to calibrate your display again.
• Not all displays are created equal. An LCD will never
match a CRT. They’re different, just as a piece of color
chalk will never match a crayon. Also, don’t expect a low-cost
display to perform the same as an expensive one. Some cheaper
displays don’t have the color gamut (think of gamut as
the palette of colors from which to choose) that will produce
the colors you want.
• Environment affects your display. Be aware of what kind
of lighting is in your digital darkroom. Keep lights off your
display. Not only can lighting affect the apparent color temperature
of your display, it also can affect the apparent contrast ratio
of your images. What color are your walls? If you want to achieve
the best results, keep the walls neutral.
Digital imaging gives you great latitude in adjusting your images.
With proper calibration of your display, you can get closer
to that acronym first championed by the word-processing industry:
WYSIWYG—what you see is what you get.
