Diaphragm (optics) photographic lens is called an iris diaphragm. In the early years of photography, a lens could be fitted with one of a set of interchangeable diaphragms , often as brass strips known as Waterhouse stops or Waterhouse diaphragms. The iris diaphragm in most modern still and video cameras is adjusted by movable blades, simulating the iris of the eye. The diaphragm has two to twenty blades (with most lenses today featuring between five and ten blades), depending on price and quality of the device in which it is used. Straight blades result in polygon shape of the diaphragm opening, while
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