How Does a Range Finder Work?

A range finder is a mechanism in cameras that allows a photographer to determine the distance to his or her subject and take a picture in sharp focus. Cameras with range finders have existed for nearly a century, as Kodak introduced this type of product in 1916 with the Kodak Autographic Special. So...how does a range finder work?

Background details

Range finder cameras were common between the 1930s and 1970s, but soon lost ground to SLR, or single-lens reflex, cameras. Range finder cameras were made in many shapes and sizes over the years, most commonly in 35mm cameras. They were considered high-end cameras and soon lost more ground to cheaper digital cameras with auto-focus. Some digital cameras are now manufactured with range finders, but they are not as common.

How it works

Most varieties of range finders show two images of the same subject, one of which moves when a calibrated wheel is turned. When the moving image and the still image overlap and fuse into one image, the distance to the subject is read off of the calibrated wheel. Older models of range finder cameras displayed this distance and required the photographer to use the value to adjust the lens focus ring. This is why it may have looked like photographers were turning a dial on their camera. If a camera does not have a range finder, a photographer can use an external one attached to the shoe at the top of the camera. As technology improved, the range finder was incorporated into the viewfinder and involved more automation. Currently, the range finder is coupled with a focusing mechanism so the image is focused correctly when the two images in the range finder fuse. By accurately determining the distance and clarity of the subject, a photographer can take better pictures.

Range finders enhance a camera's capabilities by accurately determining the distance to the subject and allowing the photographer to produce a clearer, more pristine image.