A rangefinder camera is a camera fitted with a rangefinder: a range-finding focusing mechanism allowing the photographer to measure the subject distance and take photographs that are in sharp focus. Most varieties of rangefinder show two images of the same subject, one of which moves when a calibrated wheel is turned; when the two images coincide and fuse into one, the distance can be read off the wheel. Older, non-coupled rangefinder cameras display the focusing distance and require the photographer to transfer the value to the lens focus ring; cameras without built-in rangefinders could have an external rangefinder fitted into the accessory shoe. Earlier cameras of this type had separate viewfinder and rangefinder windows; later the rangefinder was incorporated into the viewfinder. More modern designs have rangefinders coupled to the focusing mechanism, so that the lens is focused correctly when the rangefinder images fuse; compare with the focusing screen in non-autofocus SLRs.

Almost all digital cameras, and most later film cameras, measure distance using electroacoustic or electronic means and focus automatically (autofocus); however, it is not customary to speak of this functionality as a rangefinder.

Carl Zeiss (11 September 1816 – 3 December 1888) was a German maker of optical instruments commonly known for the company he founded, Carl Zeiss Jena (now: Carl Zeiss AG). Zeiss made contributions to lens manufacturing that have aided the modern production of lenses. Raised in Weimar, Germany, he became a notable lens-maker in the 1840s when he created high-quality lenses that were "wide open", or in other words, had a very large aperture range that allowed for very bright images. He did this in the city of Jena at a self-opened workshop, where he started his lens-making career. At first his lenses were only used in the production of microscopes, but when cameras were invented, his company began manufacturing high-quality lenses for cameras.

Zeiss began his life in pre-imperial Germany where he went to a grammar school, and undertook apprenticeship under Dr. Friedrich Körner, mechanic and supplier to the court. He later attended lectures in mathematics, experimental physics, anthropology, mineralogy and optics at the University of Jena. After seven years he opened a small workshop with hardly any tools. He made many lenses but had little recognition until 1847 when he hired his second and third apprentice.