The Three Little Pig (ments) Know your C,Y, M and K

Investigate how light and color interact by aligning three colored and one black overhead transparencies

Clear acetate/overhead transparency

Computer with Web access

Color printer (Make sure that your printer will print on acetate. Laser printers and inkjet printers might require different types of acetate.)

Click pr picture on a separate sheet of transparent acetate. Remember that you will probably have to insert the acetate sheets into your printer manually

If you cannot print on acetate with your equipment, see if your local copy center can help in transferring these images.

• Cyan acetate

int a copy of eachon each link below and

• Yellow acetate•

• • Magenta acetate

• • Black acetate

• • Full-color acetate

• • Optional: You can print a classroom set of images (multiple images

on the same sheet) by clicking here.

•

Align the cyan, yellow, magenta, and black acetates and hold them up to the light. (Just donít look directly into the sun.) What do you see? Align various combinations of acetates. Now, what do you see? Compare your four colored acetates to the full-color acetate.

Option: If you have access to an overhead projector, project various combinations of the colored transparencies onto a screen.

Although white light contains a rainbow of colors, our eyes are only green (G) and blue (B) light. Your brain takes thestimuli from those three colors and interprets athe other colors based on the proportion of RGB. Since human brains only processes those three colors of light, white light can be effectively described as a combination of RGB.

sensitive to red (R), ll

RGB are known as the primary colors of light. The

Black is usually used in conjunction with cyan, yellow, and magenta.

combinations of two of the three primary colors of light produce the secondary colors of light. The

secondary colors of light are cyan, yellow, and magenta. In printing,the abbreviation for cyan is "C," Yellow is "Y" and magenta is "M."

Black helps define image details. In printing, the abbreviation for black is "K." "K" is used so that it wonít be confused with a "B" for blue. You might see the initials of these colors, CYMK, in association with various printing procedures, processes, and products.

The secondary colors of light are the primary colors of pigments or

Printed materials, like the acetates, use CYMK's ability to absorb or e

dyes (not red, yellow, and blue as many people are taught). If white light interacts with the primary colors of pigments, primary colors of light are removed.

filter RGB colors to produce a multitude of other colors. This principlis called color subtraction (Your printer uses CYMK pigments and color substitution to make the pictures you print).

What happens to white light as it passes through colored acetate

Pigmecolor thatís removed pass through

nt White light or RGB color

The colors of light that

Cyan Red Blue and Green Yellow Blue Red and Green

Magenta Green Red and Blue

tes you printed for this activity have regions coated with ink (cyan, yellow, magenta, or black pigments) and other regions that are

.

The aceta

not coated or clear. The amount of pigment affects the color and intensity of the light that passes through. If a layer is held up to the light, say the cyan sheet, all colors of white light pass through theclear areas. Where it is coated with cyan pigment, red light is blocked

White light as it passes through the cyan acetate

White light as it passes through the yellow acetate

White light as it passes through the magenta acetate

If two layers are aligned, the primary colors of light may appear. For example, if a solidly colored portion of cyan acetate is held against a solidly coloredportion of yellow acetate,only green light is seen. This is because cyan subtracts red light andyellow subtracts blue light, allowing only grelight to pass through.

en

When all CYMK acetates are overlaid, depending ors and various intensities

are subtracted from the white li

n where you look on the acetates, various colo

ght. This allows one to make an infinite number of colors from different combinations of cymk. (Click here if you would like to see further examples how this works.)

of

CYMK are the colors used in printing, too!

If you align your CYMK acetate layers and place them on top of a white sheet of paper, you will still see a full- color image. Now, imagine that you could remove the acetate but leave the CYMK pigments on the white paper. You would still see a full-color image. This is because white light hits the pigments and paper and is selectively absorbed and reflected before reaching your eye.

The process that printers use to make a full color image with cyan, yellow, magenta and black is called four color printing or four color separation.

Newspapers use CYMK in their printing process. At the base of many newspapers you can see the color separation test pattern.

By Eric Muller

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