How Does a Digital Photography SLR Camera Work?

If you've ever gone camera shopping, you've probably notices that camera prices vary dramatically, from less than a hundred dollars to several thousand.

You may also have notice that any camera labeled "SLR" is includes a large jump in price.

What is a digital SLR camera? Why is it more expensive? Is a digital photography SLR camera worth the extra money? This article will explain what a digital SLR camera is, how it works, and why, if you're serious about photography, you'll want to invest in one.

Both film and digital cameras have problems that digital photography SLR cameras fix. First, have you ever taken a picture with a film camera and noticed that the photo came out slightly off center from the picture you framed through the viewfinder, particularly on close-ups?

This happens because, when you frame a picture, you're not actually looking through the lens of the camera. This is because the shutter and film (or the image sensor, in the case of digital camera) is in the way. Consequently, the viewfinder is usually up and off to the side from the actual camera lens. This results in two slightly different angles of view between the pictures you frame in the viewfinder and the photo the lens takes.

A digital photography SLR (Single-Lens Reflexive) camera fixes this problem. Through the clever use of mirrors and prisms, it allows the photographer to actually see through the lens of the camera. A digital photography SLR camera lowers a mirror into the lens box. This mirror reflects the image coming through the lens upward into a prism, which then bounces the image into the viewfinder. The camera and the photographer both see the same thing. This is the "Single Lens" that "SLR" refers to.

When the photographer snaps a picture, the mirror in the lens box flips upward out of the way. The shutter then opens and exposes the image sensor or film to light coming through the lens. The image is captures, the shutter closes, the mirror swings back down, and the photographer is able to see through the viewfinder once again. This ability of SLR cameras to automatically move the mirror out of the way for the instant the photograph is taken is the "Reflexive" part of "SLR."

Digital cameras, however, have "live preview", which does allow you to see exactly what the lens is seeing at the moment the picture is taken. Digital cameras, however, have problems of their own. The main one is "shutter lag," or the time delay between when you press the shutter button and when the picture is actually taken.

During this time, the camera is computing and setting the focus and exposure. For some digital cameras, this delay can be as much as two or three seconds. During these seconds, focus could be lost, the angle change, the camera be jostled, or the subjects being photographed may move.

Although this is not an issue for still photography, for photographers needing to capture images instantly (such as action, sport, or wildlife photographers), this multi-second delay can ruin a shot.

A digital SLR camera, however, fixes this problem as well. The mirror and prism system allows the photographer to see what the lens is seeing, including focus and lighting conditions. When the shutter button is pressed and the mirror is lifted out of the way, the digital SLR camera is already set to instantly capture the picture on the image sensor.

While even the most high-end digital cameras have a shutter lag time of at least half a second, digital SLR cameras can take between three and ten pictures per second. This is how digital photography SLR cameras combine both the accuracy and speed of SLR cameras with the convenience of a digital camera.

Although a digital photography SLR camera is more expensive than a cheap "point and shoot" digital camera, they are far faster and more accurate. Any professional photographer, or even an amateur photography enthusiast, will consider a digital photography SLR camera to be a smart investment of their money.