Pixels and Megapixels
Every picture you see on your screen is actually a bunch of little lighted dots on the screen called pixels. You don’t see the individual pixels because they’re too small, but if you take a small original picture and zoom way in, each pixel reveals itself as a small colored square. Figure 23.23 shows an example. The picture on the left is the original. The picture on the right is an extreme zoom in. There you can see how the picture is actually lots of pixels — little colored squares.
When shopping for digital cameras, megapixels are a key pricing factor. A megapixel isn’t one humongous pixel. It’s a million regular-sized pixels. The basic rule of thumb is, the more pixels, the better the quality of the pictures. The term “quality” in this context really means how big you can make it (or print it) without the picture looking pixelated. A pixelated picture looks, at best, blotchy. At worst, it looks like a bunch of pixels rather than a coherent picture.
Table 23.1 provides some general guidelines on how the number of megapixels translates to print quality. You can always print any picture at any size, of course, but you start to lose quality if you go above the recommended maximum size shown in the second column. All numbers are approximate, of course, because many other factors come into play in determining overall print ...