How does a rangefinder differ from an SLR?
SLR stands for single lens reflex, where reflex refers to the mirror. In an SLR, you are actually looking through the lens to focus. The image you see is reflected to your eyes from a mirror. In most SLRs, there is a moving or swinging mirror which has to be moved out of the way prior to exposing the film. A few SLRs have a pellicle mirror which splits light between the viewfinder and the film plane.
