About Digital SLRs

Most of the technology I've described so far applies equally to digital SLR, EVF, and optical-viewfinder-equipped cameras. (Funny how it seems easiest to differentiate the main camera types by the systems they use for viewing images!) There are some differences between how a dSLR works and how other cameras work, and you'll find all the gory details in Mastering Digital SLR Photography, also by Thomson Course PTR. However, if you're planning to purchase a digital SLR like the one shown in Figure 2.13, you'll want to keep the following technical differences in mind.

Interchangeable lenses. Digital SLRs let you remove the lens mounted on the camera and substitute another. That gives you extra flexibility in choosing optics to broaden your view or extend your reach to far-away subjects. In addition, some lenses have extra capabilities, such as image stabilization and close-up focusing that you'll find useful.

Through-the-lens viewing. A dSLR lets you view the exact image the sensor will see, without the electronic fuzziness you get in an LCD or EVF. That makes these cameras easier to use to view, focus, and compose images before you take the picture.

Better quality. A digital SLR will use much larger sensors with larger pixels, producing improved quality and lower noise than a non-SLR camera of the same (or even higher) pixel count. A 6-megapixel dSLR can easily provide better results than an 8-megapixel point-and-shoot camera simply by virtue of its better sensor.

No LCD preview. Digital SLRs use a mirror to bounce light to the viewfinder. The mirror flips out of the way at the time of exposure to let the light strike the sensor instead. That means you can't use the LCD on a dSLR to preview your picture.

Figure 2.13. A digital SLR actually uses a lot of the same technology as its non-SLR cousins.

In most other respects, however, digital SLRs are very similar to other digital cameras in their technology. They use sensors, electronic/mechanical shutters, lenses equipped with apertures to control the amount of light, circuitry to capture and store images on memory cards, and controls that are very much like those found on other digital shooters as well as late-model traditional film SLR cameras.