18% Gray Card
Cameras take pictures using available light. But each light source has a
different "Color Temperature" or "White Balance".
Sunlight if far different then incandecent lights used indoors. Tungsten Ligths
(incandescent) are yellowish. Fluorescent are bluish.
Most new cameras choose a White balance automatically but the user can override
the automatic setting. The computer chip in a digitasl camera finds the
brightest spot on the image and "assumes" that is white, it then adjusts all
It does a reasonable job, more or less but what a shock I got tonight when I
used an 18% gray card to calibrate the white balance of my camera. First of
all, all of the following photographs were taken with incandescent lights: One
in the hall to the right of the camera and one in the bedroom to the left of
the camera. No flash was used.
For subject matter I put 3 portions of grocery-store posterboards on a door. I
cut small sections of green, black and white. You all have seen the white
posterboards - really white, except in my photos below.
Camera set on Auto White Balance (AWB)
The white certainly doesn't look white to me.
Then I set the camera to "Tungsten" as the source of light, which is correct.
the white looks whiter but still has an off-cast to it.
Then I set the camera to "Fluorescent" as the source of light, which is not
Then I set the camera to "Daylight" as the source of light, which is also not
Almost orange because the camera assumed a very white source of light but in
fact, the light source is rather yellow.
Not to calibrate the white balance using the 18% gray card Sherri and Kraig got
me for Christmas - well, they got me an Amazon gift certificate which I used to
buy a "Digital Grey Kard" by Digital Image Flow.
The Canon EOS instructions are simple: Step 1) photograph the gray card. Step 2)
use the Custom White Balance menu to correct the color balance.
This is the result and I'm amazed it could make so much difference. (Forgive the
"out-of-focus". I bumped the door.
See how white the white is. While not perfect, it is by far the best in the
lot. And I had never done this before so with practice I can get better at
setting the custom white balance.