Digital SLR comes from digital single lens reflex, which is named this way because of the mirror that sits behind the lens of the camera and sends the light to the viewfinder.
The digital SLR's are designed in such a way that you can use a lot of different lenses, with different focal lengths. This versatility is the reason why digital SLR cameras are so popular among professionals. When you're using a camera that is not a SLR, you need to match the angle of the viewing lens with the angle of view. If you're doing short-range zoom or you have a fixed lens, then it's OK, but at different focal lengths it can be much more difficult. The SLR is better because the viewing and taking lens are the same.
While entry level digital SLR cameras don't always have Live View, advanced models usually do, and they let you compose the photos just like you do with a snapshot camera. The basic models will lock the mirror, and the prism will divert the image towards a sensor that is small. Then, instead of sending it to a capture sensor, it will be sent to the LCD screen, which can take down the performance a bit. If you're getting an older model you might need to focus on the image manually when you are in Live View, though contrast autofocus is available in newer digital cameras.
Digital SLR Camera Types
Digital SLR With Interchangeable-lens
These models are those considered as SLR's by most people. They're also the ones that we'll be talking about in this article. Just like the name says, in these SLR cameras you can change their lenses. This way you're able to switch from a supertelephoto lens to an ultra wide angle.
Examples: Basically, most digital SLR cameras that are sold today belong to this type.
Digital SLR With Fixed Lens
On these digital SLR's, the versatility is limited by the fact that you can't change the default lens. The mirror that bounces the light towards the viewfinder is nonmoving and semi-transparent in most of these models.
One example of a camera with fixed lens is the Olympus E-20N
Camera similar to SLR's
Cameras that look like digital SLR cameras are usually digicams that have either an optical finder or a small LCD. You can't consider them as digital SLR cameras since the mirror is missing, and the quality of the photos isn't even close to what you can do with a true SLR. Usually, this type of camera has a very long zoom, and another name for them is magazooms or ZLRs.
