The Photoshop Toolbar is shown on the right. I shall refer to tool positions in the row-column (spreadsheet) format. The uppermost tool on the right, then, shall be located at R1-C2 (row one column two)

Scanning:
Scanned images are in “bitmap” format, composed of individual dots (pixels). Each pixel has color information. The amount of color information per pixel depends on the “color depth” that you assign to it. Early color computers had “8-bit” color, meaning that they could display 2 8 , or 256 colors. 8 bits = 1 byte (the common gauge of computer memory. The resolution of an image is the density of pixels, typically given as pixels/inch (or “dpi” – dots per inch). The size, resolution, and color depth determine the file size. For example, a 3” x 6” photo at 72 dpi in 8-bit (1-byte) color yields a file size = 3 x 72 x 5 x 72 x 1 = 77,760 bytes (or 75.9 kilobytes). The 75.9 vs. 77.8 discrepancy is due to the fact that orders of magnitude in the computer world are based on the binary system. Thus a “kilo-” (10 3 to us) is approximated by 2 10, or 1024. Modern “true-color” monitors and graphics cards support 24-bit color (or higher), assigning 2 24 (16,777,216) colors to each pixel. The file size becomes 24 times as large (1.78 Megabytes). If we wanted to match a 600 dpi printer resolution at 24-bit color, the file size would be a whopping 123 Megabytes, if saved in straight bitmap (BMP) format. Graphical compression algorithms can cut down the file size significantly (JPEG is the best at the present time). Scan at the resolution that fits your intended use. If you want to use a photo in a computer presentation, and a 15” monitor is run at 1024 x 768 pixels, the pixel density is about 85 pixels/inch (if you want the photo to appear at about the same size on the monitor). The appropriate resolution for a printed image is determined both by the printer resolution and by the screen frequency or lines per inch (lpi) of the halftone screens used to reproduce images. You will have to look this up for your printer.

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