TECH TIPS
Color My World
Methods for Gauging Hues Accurately
by Bill Stetz
In the editing environment, Color Management does not seem high on the list of daily work-related maintenance. Unless your are a colorist, rather than an editor, calibrating your system for color conformity is not paramount but perhaps last on the list of things to worry about in your day-to-day. But with a basic understanding of how your color output devices work and some calibration techniques (either software- or hardware-based), you can perform very basic or expressive changes in your non-linear editing (NLE) files to improve the look of a scene here and there or provide a “look” to a sequence or entire project.
If, like me, you dread another layer of complexity in any workflow process and you think that a new software package is the last thing you want to learn before getting on with your next project, join the club. I will try to lay this out as simply as possible and you may decide for yourself if you want to tackle a new area of computerese. A little background is in order.
A Miniscule Primer
Computer monitors, like television receivers and film technology,
are all based on the RGB (Red, Green, Blue) color model. To add some
relevancy, there are many ways or systems of describing and reproducing
color, RGB being just one. The printing industry uses CYMK (Cyan,
Yellow, Magenta, Black). By mixing color (inks) in the CYMK gamut,
printers are able to reproduce a fair amount of the color spectrum
on paper, the reflective color environment. And outside of this discussion,
printers may use fifth, sixth or more additional inks to increase
their color gamut or reproduce colors impossible to create strictly
within the CYMK system.
A gamut is the finite universe that a particular system of color is able to display. RGB, CYMK and other systems are not capable of reproducing all the same colors or as great a range of color. To bottom-line this concept, certain colors that you can reproduce in the RGB environment may not reproduce well in the CYMK environment and vice versa. Most colors overlap all gamuts but some just cannot be reproduced as a constant from one system to another. A close––or many times not-so-close––match is the nearest thing you may get for colors moving from one system to the other.
Output Devices: TVs, Monitors, Film Projection
In the world of NLE, television, video and film projection–our
world–RGB is the system with which we have to contend, or manage.
Color management is the basis for delivering the intended and consistent
product to the audience. Theoretically, color management may start
or continue anywhere in the creative process of a project. It may
begin with the director’s concepts, the camera operator’s
tweaks, the lighting director’s approach, or with the colorist,
the editor, the digital internegative process (film or video) or the
final print (film).
When you buy a monitor for your system, it is supplied by the manufacturer with a default look-up table that maps how a particular color is displayed. Here is where the management begins. That look-up table may interpret a color that may not look like it should. You, the user, can profile the monitor to display color in another or more accurate way. This is why that if you work on files, sequences or video on one computer system it may look subtly or vastly different when displayed on another system. Profiling allows the operator to calibrate monitors to look the same or close to the same on any systems that the files are displayed.
Profiles may be changed simply using color profile software that is adjusted visually by the operator. This entails comparing generated shades of reds, greens and blues to samples the software provides to adjust the monitor to perceptual standards. Profiles may be changed automatically using profiling software/hardware combinations that measure the color coming out of the monitor using devices called colorimeters or spectrophotometers. In the film processing industry, devices known as densitometers are used to measure the transmission quality of film in various densities or spectrums to make adjustments to the timing of scenes.
Limitations of Monitors
The cause of limitations to perfectly match one monitor to another
may be caused by age of the monitor (age wears things out, right?);
the differing manufacturer specs (different brands of monitors may
not match because of the technology that was used to design them);
the type of device (LCD monitors and CRT monitors have different qualities)
or the viewing environment (viewing the same monitor in a brightly
lit room and a dark room can have different effects on the viewing).
Practically speaking as of 2005, cathode ray tube (CRT) monitors have
a much greater ability to reproduce color under all conditions than
liquid crytstal display (LCD) monitors. Even a CRT monitor costing
$200-$300 can display a wider gamut more accurately and outperform
an LCD monitor costing $1,000-$2,000.
Although new technologies are closing this “color gap,”
a large-box, heat-producing, power-hungry, heavy CRT is a better color-viewing
device. For detailed color work, which most editors are not obliged
to consider, a CRT type monitor is essential. Still, when the director
looks at your screen and says the red blouse on the heroine in his
or her film looks more pink than red, you can attribute that to the
LCD monitor you’re using instead of a CRT monitor, or the lack
of monitor profiling––or both. The final work displayed
from a DVD player on a good video monitor may relieve the distress
the director had about the red blouse looking pink, but you may not
be able to convince that director that the blouse color is right if
your monitor shows pink in the editing room.
Considerations
If so many factors affect the color of your program material in the
end, where do you start? If color is to be adjusted at all, you can
only start by making sure that any subjective or creative changes
made in the editing stage or colorist stage are based on a clean,
well-calibrated system. The source material is what it is. From then
on it all becomes a matter of discernable taste and changes made to
satisfy that taste based on known or trusted standards of what you
see on your NLE monitor. What your audience sees in the end is what
they see. That is, in the end you have no control over the audience’s
viewing device or the process in between, but you can start from a
reasonably solid beginning by calibrating your hardware and calibrating
often as devices change based on age, heat-up, viewing conditions
and inadvertent operator color adjustments.
Software-Only Calibrators
Using simple profiling software already on your machine, or easily
found, is the easiest way to set up your viewing device. These calibration
programs are based on the viewer’s perception of comparison
tests. I find these calibrations better than no adjustment, but do
not expect them to be as repeatable as software/hardware calibration
techniques that use colorimeters or spectrophotometers.
The most commonly available profilers are the Apple Colorsync calibrator
(Mac) in the system preferences on OS X or Adobe Gamma for Mac, PC
and other systems that run Adobe PhotoShop.
The process is this: Using Mac OS X, go to the system preferences.
Under the Hardware heading, click Displays. The default window will
show the resolutions of your screen for selection. Click on Color.
This will display a list of all the profiles stored on your machine,
any of which may be selected for use here (see figure 1).
(Note: Your display profiles are typically stored in Macintosh HD > Library > ColorSync > Profiles > Displays. If you do not find them there for some reason, search your hard drive for files with an .icc extension. Old profiles can only be deleted from the folder directory they are in. Normally, there are no software commands within applications for deleting profiles.)
Click on the button labeled calibrate. This launches the Display
Calibrator Assistant opening window (see figure 2). Click in the box
labeled Expert Mode to run more adjustments. Click Continue. Figure
3 shows the first adjustment screen for determining the native gamma
response. By adjusting the small node in the left model up or down,
you visually match the brightness of the center-outlined apple shape
until it matches the brightness of the surrounding area of the containing
box.
Note: When calibrating LCD screens only, take caution to view your
monitor “square on” or perpendicular to the center of
the screen. If you view the screen from the top down, bottom up or
from one or the other side, the colors and brightness of colors will
not appear accurate to your eye. This is function of the LCD screens.
CRT monitors do not suffer from this anomaly.
After you have adjusted the brightness of the left model to blend with its background, use the control node of the right model to adjust the color hue of the outlined apple to match the color hue of its surrounding background. Click continue.
Next follow the same procedure four more times on four separate window
panels. Click continue.
This following panel is the target gamma setting. Macs are usually
preset for a gamma of 1.8 and PCs and televisions are targeted for
a gamma of 2.2. Set your gamma for 2.2 whether you are on a Mac or
a PC. The gamma is the contrast or response curve of your monitor.
A higher gamma represents higher contrast in your picture. Click continue.
The next panel (figure 4) adjusts your target white point. One would
think that white is white, right? No. White in daylight is much more
blue than white under incandescent light. White in shade is much more
blue than the white of daylight. White point is measured as the color
of a theoretical ‘black’ body raised to the Kelvin temperature
stated. Thus standard daylight is sometimes stated as 5000º Kelvin
or 6500º Kelvin depending on what your application is. We will
use 6500º K. But note that as you adjust your white point from
lower to higher, whites will appear warm or yellowish to cool or bluish.
The higher the Kelvin color temperature of your light source (or monitor
basis) the bluer it gets thus affecting how all colors under the same
light or in the same environment are rendered. Click continue.
The next panel (figure 5) asks if you want to share your profile with
other users who may log into your computer. You may check to approve
this or keep your profile to load only when you log in. Click continue.
The last panel (figure 6) asks you to label the profile you just made to save the profile. It will appear as this name in the list of available profiles. Good practice in making the name of the profile relevant to the monitor used and the date of calibration keeps your profiles organized and easily applied to particular uses. Click continue.
The last panel summarizes your calibration session settings and the characteristics. You’re done. The new profile is automatically put into effect.
Software-only calibration resources:
Apple ColorSync calibrator (system utility), under system preferences/displays
Adobe Gamma (PhotoShop utility, MAC & PC) comes with PhotoShop,
http://www.adobe.com/support/techdocs/321608.html
Monitor Calibration Wizard (freeware download, Windows),
http://graphicssoft.about.com/gi/dynamic/offsite.htm?site=http://www.hex2bit.com/products/product%5Fmcw.asp
EasyRGB
http://www.easyrgb.com/calibrate.php
Whether you do visual software based profiling or use colorimeters to build profiles for your monitor set-ups, calibrating and calibrating often will avoid surprises later in work that is passed on for finishing. Try managing your color, especially if you make any creative or correctional adjustments in any of your work. The more you understand the color management process, the more valuable your work becomes.
Bill Stetz is art director of the Editors Guild Magazine. He’s taught Motion Graphics at the Art Institute of California in Santa Monica, CA and uses color management for professional photography, print and video applications. He may be reached at design@clik.net.
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