Diaphragm (optics) the lens. The centre of the diaphragm's aperture coincides with the optical axis of the lens system. Most modern cameras use a type of adjustable diaphragm known as an iris diaphragm, and often referred to simply as an iris. See the articles on aperture and f-number for the photographic effect and system of quantification of varying the opening in the diaphragm. A natural optical system that has a diaphragm and an aperture is the human eye. The iris is the diaphragm, and the opening in the iris of the eye (the pupil) is the aperture. An analogous dev in a
The Seeing Eye through the training of guide dogs in the United States. Eustis and Humphrey began to research and modify their own training in which they trained several German shepherds to guide humans. In April 1928, Frank met his first ever Seeing Eye dog named Kiss. He changed her name to Buddy and named all his future Seeing Eye dogs (he had six in total) Buddy. The name is now retired by The Seeing Eye. Frank and Buddy had to go through a six-week training that not only created a strong bond, but also taught them to work as a team to