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
Crus of diaphragm Crus of diaphragm The crus of diaphragm (pl. crura), refers to one of two tendinous structures that extends below the diaphragm to the vertebral column. There is a right crus and a left crus, which together form a tether for muscular contraction. They take their name from their leg-shaped appearance – "crus" meaning "leg" in Latin. The crura originate from the front of the bodies and intervertebral fibrocartilage of the lumbar vertebrae. They are tendinous and blend with the anterior longitudinal ligament of the vertebral column. The medial tendinous margins of the crura pass anteriorly and medialward, and meet in