Graphics Programs Reference
In-Depth Information
FREQUENTLY ASKED QUESTION: COLOR CHANNELS AND B&W
Why should I make changes to a photo's color channels when I'm creating a black-and-white im-
age?
Back in
Chapter 7
, you read about how photos consist of three separate color channels: red, green,
and blue. In your camera's original file, each of these channels is recorded as variations of light
and dark tones—in other words, as a black-and-white image. This image file tells your computer
or printer to render a particular channel as all red, blue, or green, and then blend these three
monotone channels to make all the colors you see.
When you convert a photo back to black and white, each of these channels contains varying
amounts of details from your photo, depending on the color of your original subject. So the green
channel might have more detail from your subject's eyelashes, while the red channel may have
more detail from the bark on the tree she's standing under. (Remember, the color channels them-
selves don't necessarily correspond to the color of the objects you see in the final photo. Or, put
another way: Your camera uses a mixture of red, green, and blue to create what look like eye-
lashes, bark, and so on to us humans.) And there's often more
noise
(graininess) in one channel
than the others.
The “Convert to Black and White” dialog box's Red, Green, and Blue sliders let you increase or
decrease the presence of each color channel so you can adjust how prominent various details are
in the photo. These adjustments can greatly change the appearance of the final black-and-white
image. (The Contrast slider, not surprisingly, adjusts the contrast—
Contrast
—of the combined
channels.)
That's the theory behind those color-channel sliders, but fortunately, you don't have to understand
it to use them effectively. Just be sure you have a good view of your photo (zoom in and, if neces-
sary, move the dialog box), and then move the sliders till you're happy with what you see. If you
plan to print your converted photo, the Tip on
Tip
has some info on how to get a good black-and-
white print from a color inkjet printer.
Removing Color from Photos
Because one size never fits all, Elements gives you a few other, totally different ways to re-
move color from images. The instructions in the preceding section are usually your best bet
when converting a whole photo to black and white. But if you're in a hurry or you're looking
to do something artistic, like change a color photo into a drawing or a painting, try one of
these three methods:
