Section 4 | Page 4

Additive Color vs. Subtractive Color

Video monitors use the additive color system. Offset printing uses the subtractive color system. Computer screens display a larger gamut of colors than can be produced on press and by most color printing devices. This is important to know when using the computer as a design tool. The color you see on your computer monitor is probably not what you will get when the job is printed.

The limitations of the offset printing (subtractive) process are due in part to the image screening process and in part to the type of paper used to print the image. The screening process converts an original continuous-tone image, such as a color photograph, into a small pattern of dots for each process color so the image can be printed with a pigment (wax, toner, ink) or dye on paper. A

continuous-tone image shows a continuous density range between darker and lighter areas. An ink-printable image (screened image) is made up of small dots which create the illusion of lighter and darker tones. A screened image can be produced using a fixed grid pattern of different-sized dots, or by varying the number of randomly placed, same-size dotsùor a combination of the two.

See Figure