Diaphragm (optics) 1889 "Dictionary of Photography" (see figure), but disappeared after Ernst Abbe's theory of stops unified these concepts. According to Rudolf Kingslake, the inventor of the iris diaphragm is unknown. Others credit Joseph Nicéphore Niépce for this device, around 1820. Mr. J. H. Brown, a member of the Royal Microscopical Society, appears to have invented a popular improved iris diaphragm by 1867. Kingslake has more definite histories for some other diaphragm types, such as M. Noton's adjustable "cat eye" diaphragm of two sliding squares in 1856, and the Waterhouse stops of John Waterhouse in 1858. Diaphragm (optics) In optics, a diaphragm
Diaphragm (optics) by using an automatic ND filter. Unlike a real diaphragm, this has no effect on depth of field. A real diaphragm when more-closed will cause the depth of field to "increase" (i.e., cause the background and the subject to both appear more in-focus at the same time) and if the diaphragm is opened up again the depth of field will "decrease" (i.e., the background and foreground will share less and less of the same focal plane). In his 1567 work "La Pratica della Perspettiva" Venetian nobleman Daniello Barbaro (1513-1570) described using a camera obscura with a biconvex lens as a