Lecture 05.01: Color Models


As design­ers, you will need to work across mul­ti­ple media for­mats, regard­less of the indi­vid­ual projects final form. Even print media requires the con­ver­sion from one color model to another.


Use infor­ma­tion pre­sented here to prop­erly scan images for use in a pro­fes­sional setting.

Background Reading

Koenig, Chap­ter 6 and 8. Dab­ner, Mod­ule 5, Unit 4 and 5


Tele­vi­sions, scan­ners, dig­i­tal cam­eras and com­puter mon­i­tors use this color model. Often referred to as “addi­tive” color because red, green, and blue light added in equal amounts are per­ceived as pure white and the absence of light as black. Com­bin­ing these three col­ors will cre­ate a range of sim­u­lated col­ors on screen.

RGB Picker from Photoshop Color Dialogue Box

Hexadecimal (WWW)

A sub­set of RGB color, web safe col­ors are 216 col­ors that are avail­able to all com­puter plat­forms. The key­ing of the col­ors ensures accu­rate color between images and HTML documents.

Hexadesimal Picker from Photoshop Color Dialogue Box


In com­mer­cial and desk­top com­puter print­ers, translu­cent cyan, magenta, yel­low, and black ink or toner is added to the printed sur­face. Often referred to as the “sub­trac­tive” color model, the color par­ti­cles absorb and reflect light. We per­ceive dif­fer­ent col­ors because dif­fer­ent inks reflect and absorb light dif­fer­ently. Pure dots, placed in a rosette pat­tern, sim­u­late color to the eye.

Process Picker from Photoshop Color Dialogue Box

Spot Color

Add spot color here.

Spot Picker from Photoshop Color Dialogue Box

Color Gamut

The vis­i­ble spec­trum con­tains mil­lions of col­ors. Each device and process in design repro­duc­tion uses a unique sub­set of this range known as its color gamut. Color gamut over­lap, but do not match. Some col­ors vis­i­ble on screen will not be avail­able on paper, or on a par­tic­u­lar com­puter platform.

Arrow Points to Out of Gamut Icon, Color Picker from Photoshop Color Dialogue Box

Bit Depth

Each pixel in an image has a color value assigned to it. This value is known as its bit depth. Black and white images, such as lin­eart TIFF images, have a sin­gle black or white value. RGB, such as GIF images, have 8‑bits of total val­ues for red, blue, and green result­ing in a 256 color range. If more mem­ory is allo­cated to each pixel, 8‑bits for each red, blue, and green, then 24-bit true color is avail­able, result­ing in mil­lions of colors.

1 bit, Lineart Sample8 bit, color sample24 Bit, Color Sample

File Size

There is a rela­tion­ship to file (K or kilo­bytes, Mb or megabytes and G or Giga­bytes) size based on the res­o­lu­tion (dots per inch, or dpi), the color mode (RGB, etc), and the phys­i­cal dimen­sions (height and width). Any change in any of these traits will alter the file size and image qual­ity of the document.