A rangefinder is a camera focusing system that helps photographers achieve sharp images by superimposing two images in the viewfinder. When the images align, the subject is in focus. Originally a mechanical or optical device, modern rangefinders often use digital technology for greater accuracy and ease of use. Rangefinders are valued for their precision and are commonly found in both classic film cameras and some digital models. Their design allows for fast, accurate focusing, especially useful in low-light or candid photography situations.