SLR uses a technology called semi automatic moving mirror system by which the photographer sees exactly through his lens what he wants to capture. Before the advent of SLR the photographer was not able to see exactly the pictures that he wants to shoot. In these cameras there is an auto focus system which automatically focuses on the object which the user wants to shoot, they do have manual focus also which gives you a choice to select your own focus.

Before the development of the SLR, all the cameras has two optical light paths and because of this the viewfinder and the lens do not share the same path for which what the photographer sees through the camera was not the exact image of what he is going to shoot. With the coming of the SLR Technology this drawback has been taken care of.

SLRs are expensive cameras and are used by professional photographers. They are expensive but they have brought a revolution in the filming technology because of which they are preferred by many. They have brought so much clarity in the pictures to view at.