Diaphragm (optics) curved blades improve the roundness of the iris opening. In a photograph, the number of blades that the iris diaphragm has can be guessed by counting the number of diffraction spikes converging from a light source or bright reflection. For an odd number of blades, there are twice as many spikes as there are blades. In case of an even number of blades, the two spikes per blade will overlap each other, so the number of spikes visible will be the number of blades in the diaphragm used. This is most apparent in pictures taken in the dark with small
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