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Photoshop® CS4 Bible by Dan Moughamian, Simon Abrams, Stacy Cates

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1.4. Summary

This chapter described the characteristics and types of digital images, getting images into Photoshop, and storing digital images. Following are key concepts:

Digital images contain pixels, usually square in shape, that describe their colors and brightness levels. It is important to be familiar with the specific terms Photoshop uses to describe brightness levels and color qualities. Brightness, lightness, luminosity, and luminance describe the dark to light qualities in an image, separate from the color qualities. Tonal range, or dynamic range, is the range of dark to light values in an image, usually referred to as shadows, midtones, and highlights. Hue refers to the color in an image, such as red, orange, or green. Saturation is the strength or purity of a color.

Characteristics of digital images include bit depth, bitmap or vector, color mode, color space, and file format. The images can originate from numerous sources, including digital cameras, film cameras, scanners, the Internet, e-mail, and camcorders. Digital images can be stored on numerous types of media, including internal or external computer hard drives, DVDs, CDs, and USB Flash drives.

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