Web Design in a Nutshell, 3rd Edition

Gamma (Monitor Brightness)

Gamma refers to the overall brightness of a computer monitor’s display. In more technical terms, it is a numerical adjustment for the nonlinear relationship of voltage to light intensity—but feel free to think of it as brightness. The default gamma setting varies from platform to platform. Images and pages created on a Macintosh generally look a lot darker when viewed on a Windows or Unix/Linux system. Images created on a Windows machine generally look washed out when seen on a Mac. The higher the gamma value, the darker the display. Table 28-3 shows the standard gamma settings for the major platforms.

Table 28-3. Common default gamma settings

Platform	Gamma
Macintosh	1.8
PC	2.2
Unix	2.3-2.5

Because the vast majority of users are viewing the Web from the Windows environment, gamma differences are of particular concern to developers who are designing pages and graphics on a Macintosh. However, if you are designing under Windows and anticipate a large percentage of Mac traffic to your site (such as a site for graphic designers), be sure to test your pages under Macintosh gamma conditions.

Both Adobe Photoshop and Macromedia Fireworks have controls for simulating the gamma of alternate platforms. In Photoshop, select View → Proof Setup → Windows RGB or Macintosh RGB. In Fireworks, select View → Windows Gamma if you are on a Mac or vice versa. These adjustments affect only how the image appears on your monitor; they do not in any way affect the actual ...