BLACK AND WHITE POINTS
Tips by Tom
computer monitors come from the factory
preset for an office
working environment which may not be ideal for viewing and editing
61966-2.1 standard specifies a color temperature of
6500°. Most monitors have provisions for setting color temperature
using on-screen menus. Be sure to set monitor color temperature before
calibrating with Adobe Gamma or QuickGamma.
sure your display is configured for 24-bit
color. With 16-bit color there is not enough color depth to calibrate
properly. Let your monitor warm-up for at least 15 minutes before
the patches marked 0 and 10 in
appear to be the same? If they do then you need to calibrate your
monitor black point. Do the patches marked 95 and 100 appear to be the
same? If they do then you need to calibrate your monitor white point.
can calibrate black and
white points without
any special software, just the monitor settings for brightness and
contrast. Usually for ® Samsung SyncMaster 740N LCD monitor the
brightness is about 39 and contrast is about 51. It takes just a few
minutes to make these
adjustments. As a reward you will view images on the web as they were
designed to be viewed. If you're a web designer, or share images with
others, then it's imperative that you calibrate your system to a
standard. For the web or email use the sRGB
Black point calibration
should be able to distinguish between the patches marked 0 and 10 in
the above grayscale. Patch 0 should be perfectly black, matching the
unscanned portion of your monitor, and patch 10 should be barely
visible. In this section you will adjust monitor brightness so the
black point is properly calibrated.
Gamma, and several web sites, attempt to adjust the black point with
grayscale patches. However, the quality of monitor displays varies
significantly, and attempting to read something out of low-valued
patches is fraught with difficulties.
the black point is properly set, an RGB value of (0,0,0) will appear as
true black on your monitor. Increase the RGB value slightly and you
should see a slight increase in intensity. The non-scanned area
surrounding the displayed image is an ideal reference for the black
point. The goal is to make display value (0,0,0) match the black of the
adjustments to be accurate you need to use consistent lighting when
viewing your monitor. The black point for a brightly-lit room will be
higher than a dimly-lit room. After setting room lights to your
standard, minimize any on-screen applications (including your browser).
If there are bright-colored icons on your desktop, move them to a
folder and minimize the folder. You can easily retrieve them later. It
is very important that your screen be completely black.
White point calibration
should be able to distinguish between the 95% and 100% patches in the
above grayscale. If they appear to be the same, then contrast is too
high, and highlights are blocked. Most monitors work fine with contrast
set at 100%. If you find this too bright, or highlights are blocked,
decrease contrast and recalibrate the black point.
CHECKING AND CALIBRATING MONITOR GAMMA
right, from the start
If you haven't already done
so, calibrate your display before you go any further. Most monitors can
do with a bit of help in showing correct colour and tonal range.
The little bit of
time spent calibrating your monitor now will make
matching your printer to your screen easier, and save you a lot of
frustration, re-scanning and adjustment later on.
Check out your
present monitor 'gamma' with the exclusive 'Gamagic' estimator.
To use the estimator below, sit well back from your monitor and half
close your eyes. Then
look for the place
where the squares lose their colour, and are most closely matched to a
neutral grey tone. The number beneath that section tells you the
approximate gamma of your monitor.
The "Gamagic" gamma estimator.
(You saw it here
If the gamma of your system appears
to be outside the 'norm' of 2.2, then you should adjust it.
If you have a full
version of Adobe
Photoshop ®, it comes with a little utility called Adobe Gamma
®. You can use it in conjunction with the adjusment squares, and
just ignore the imprecise Adobe test patterns. In particular, Adobe's
instructions for setting the brightness level lead to a very poorly
defined black level.
One good feature that Adobe gamma does have, is the ability to save
settings, allowing you to quickly switch between gamma values, colour
On Windows ® control panel
double click on Adobe Gamma ®
icon to load it. Please
choose a target gamma from the following list depending on your
operational system *
* For PC we recommend Gamma 2.2
* For MAC we recommend Gamma 1.8
Follow Adobe Gamma instructions
adjusting gamma with the new window that you has been loaded. When you
return to this page to check out it.
If you've set up the gamma of your monitor correctly you should be able
to distinguish most of the steps of this greyscale from their
respective black or white backgrounds.