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1.7 IMAGE COLOR | ||
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When you view a natural scene, or a well done photographic color print, you are able to differentiate millions of colors. Digital images can approximate this color realism, but whether they do so on your system depends on its capabilities and its settings. How many colors there are in an image or how many a system can display is referred to as color depth, pixel-depth, or bit depth. Older PCs are stuck with displays that show only 16 or 256 colors. However, many newer systems include a video card and a monitor that can display what's called 24-bit True Color. It's called True Color because these systems display 16 million colors, about the number the human eye can discern.
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24-bit color makes it possible to display over 16 million colors. |
| TIP: Checking Your System
You may have to set your system to full-color, it doesn't happen automatically. To see if your Windows 95/98 system supports True Color, display Window's Start menu, click Settings, and then click Control Panel. Double-click the Display icon to open the Display properties dialog box. Click the Settings tab on the dialog box and check the Color palette setting. |
How do bits and colors relate to one another? It's simple arithmetic. To calculate how many different colors can be captured or displayed, simply raise the number 2 to the power of the number of bits used to record, display, or print the image. For example, 8-bits gives you 256 colors because 28=256. Here's a table to show you some other possibilities.
| Name | Bits per pixel | Formula | Number of colors |
| Black and white | 1 | 21 | 2 |
| Windows display | 4 | 24 | 16 |
| Gray scale | 8 | 28 | 256 |
| 256 color | 8 | 28 | 256 |
| High color | 16 | 216 | 65 thousand |
| True color | 24 | 224 | 16 million |
Some cameras and scanners will use 30 or more bits per pixel. These extra bits are used to improve the color in the image as it is processed down to its 24-bit final form.
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| Black and white images require only 2-bits to indicate which pixels are white and which are black. | Gray scale images need 8 bits to display 256 different shades of gray. | Color images are displayed using 4 bits (16 colors), 8 bits (256 colors), 16 bits (65 thousand colors) called high color, and 24 bits (16 million colors) called true color. |
Color depth is important at both ends of the spectrum. It's smart to match an image's color depth to the planned use. For example, if an image is to be printed, 24-bit color for colors to be bright and sharp. However, if an image is to be posted on the Web, most people are still using 256 color displays. Posting images with millions of colors will take them longer to download because the files are larger.