The Textbook of Digital Photography - PhotoCourse

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What is a Digital Photograph?...1

This book is about digital photography and understanding the end product,

the digital photograph, is a good place to begin. It is all about dots.

Photographs have always been made up of minute dots whether silver crys-

tals in film or halftone dots on a printed page. Digital cameras have just taken

this dot-like quality to a new level by electronically converting a scene into

millions of dots almost instantly and then using computer power to organize,

edit, enhance, store, and distribute them.

In digital photographs the millions of dots captured by the camera are called

picture elements—commonly called just pixels. Like the impressionists

who painted wonderful scenes with small dabs of paint, your computer and

printer use these tiny pixels to display or print photographs. To display them,

the computer divides the screen into a grid of pixels, each containing a red,

green and blue dot—called subpixels. It then uses the values stored in the

digital photograph to specify the brightness of each of the three subpixels and

the combined brightnesses of the pixel are perceived as a single color. Prints

are made in a related way, but using a different set of colors and many more

dots of color are blended for each pixel. To see these dots for yourself, use a

magnifying glass to examine your computer’s monitor and a color photo in a

magazine, book, or newspaper or use a photo-editing program to enlarge an

image on the screen until the pixels show.

This reproduction of the

famous painting “The

Spirit of ‘76” is done

in jelly beans. Think

of each jelly bean as

a pixel and it’s easy

to see how dots or

pixels can form images.

Jelly Bean Spirit of ’

courtesy of Herman

Goelitz Candy Company,

Inc. Makers of Jelly

Belly jelly beans.

Click to see how pixels

are printed using dots of

colored ink.

A photograph of an

eyeball (top) with its

pixels showing (middle)

and screened for

printing (bottom). Art

courtesy of webweaver.

nu.

whAt is A digitAl photogrAph?