The best part of Web imaging is that, in contrast with print publishing, there is no economic penalty for using images — in full color, no less — and the number of images you publish is limited only by your time and server space. And color reproduced on the computer screen is true color, whereas color in print is simulated, typically through a four-color process. Color images on the monitor are more vibrant because the color shines out from the screen, whereas color on the printed page receives its intensity from reflected light. On the down side, because every monitor is different, images that look great on your monitor may look dark or washed out on another.
The biggest drawback of screen images is resolution: both the spatial dimensions of the screen and the low resolution of computer monitors. Computer monitors are oriented horizontally, with a 4:3 ratio (640 x 480, 800 x 600, 1024 x 768). This fixed proportion can be extremely limiting if you think of the screen as a canvas: imagine Henri Matisse having only one size canvas to work on, and then only in landscape orientation.
The horizontal aspect of the screen presents design challenges, particularly when displaying vertical images.
In addition, images must share the screen with such other page elements as text and navigation links.
In addition to displaying within the limited size and aspect of the standard computer monitor, content images must share the screen with site graphics and navigation links.
Added to spatial restrictions is the fact that the resolution of the computer monitor is coarse in comparison with printed materials. Put simply, this means that there are fewer sample points available to represent an image on screen than in print.
The pixel grid of the computer screen is much coarser than the halftone grid of printed images, which means there are fewer samples available to represent an image.
As a result, images that require sharp detail in order to be understood, such as a lever on a piece of equipment or the fine outlines of a sketch, don't fare well onscreen.
Given these drawbacks, designing meaningful images for the screen can be a challenge. If you scale an image to fit the screen, you may not be able to show enough detail for the image to be useful. If you leave your image large so that the details are clear, you force users to scroll to see it all. As you gather images for your Web site, keep these limitations in mind. Choose images that fit comfortably within your page design and that do not rely on fine details to be understood. And don't get discouraged: although it may seem limited in many ways, the Web is still a great way to get images into the hands (or onto the screens) of your students.
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