Gray Chip Chart

Koz's Calibration Corner

Gray Scale or Chip Chart

800:600 Chart over a gray web page.

800:600 Chart over a gray web page--2-up for side by side monitors.

gray4_rgb_800x600.jpg Download the big chart.

gray4_rgb_640x480.jpg Download the regular chart.

gray4_rgb_720x480.jpg Suitable for Video Import.

Gray Chip Chart Specifications

This chart is available in four versions. An HTML page with the large
chart over neutral gray, downloadable 800:600 for computers
downloadable 640:480 for computers
and downloadable 720:480 for video systems.

All three chart values range from 0, 0, 0 to 255, 255, 255 (RGB) so either you
or your video system must be able to convert it to 16...235 video colorspace
if needed.

The gray patches are either 25 or 26 gray values away from each other.
They're "linear".

--Version 1.2 4/25/05--


The Gray Chart can be used for a number of different tests.

---Video Waveforms

Because the gray values progress linearly from black to white, the
display on a waveform monitor should be two straight staircases crossing
in the middle like a big "X".

If not, there may be a gray translation or
gamma problem somewhere

---Monitor Inspection

This chart has 11 digitally-generated neutral gray
patches and a neutral background. If the chart doesn't look gray
on your monitor, there's something wrong.
Off color whites or blacks or an overall color cast, if not
extreme, can be corrected by adjustments inside the monitor,
"secret handshake" adjustments from the front of the monitor,
or a software adjustment.

Individual patches exhibing a color cast not shared by their
neighbors could mean a damaged video board and probably not
a monitor problem. If your monitor is older than you are, you may
have a picture tube that's so tired that it displays three color
errors; bluish whites, greenish grays, and a redish black, for example.
There is no known cure for this. You need a new monitor.

---Monitor Matching

Display this pattern on all your monitors at the same time. Do they
all look the same? This isn't a tutorial on how to gray balance your
monitors, but yes, they should.

---Black Level Adjustment

Look at the dark bar in the center of the chart. This bar has
broad zebra stripes of 5 percent gray over dead black.
Adjust the brightness (the "sunshine" control) on your monitor
down until the entire bar is black, then up until
you can just see the stripes. Display that bar as large as you can.
Big is good. If you never see the zebra stripes, or they're
way too bright always, then the monitor is
adjusted wrong inside or the system "gamma" may be set wrong on your Mac.

---Daylight Balance

Do you think your monitor is adjusted for 6500 degrees
Kelvin [daylight] as it probably should be? Look at the web page version
of the test or download one of the charts and display it
as close to your full monitor size as you can with a gray, black or white boarder to
make up the difference.

a Turn off the lights and open the blinds to all the windows in the computer
room on a bright sunny day between 10 A.M. and 2 P.M. (You Pacific North-Westers
may be out of luck on this one) Assuming no billboards or brightly painted
walls, the outside sunlight color is now very close to 6500. Back away from
the monitor until it's just a very small part of your vision so the screen
doesn't "take over" your eyes.

Compared to the room and the outside sunlight, a 6500 monitor will look very
close to neutral, a 9300 or worse monitor will look very blue. A
3200 [tungsten] monitor will look very orange. Tungsten balanced monitors
usually aren't much of a mystery since they look weird to most people. TV sets
are generally shipped very blue so many people see that as "normal".