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 Eye in the Door The Eye in the Door The Eye in the Door is a novel by Pat Barker, first published in 1993, and forming the second part of the "Regeneration" trilogy. "The Eye in the Door" is set in London, beginning in mid-April, 1918, and continues the interwoven stories of Dr William Rivers, Billy Prior, and Siegfried Sassoon begun in "Regeneration". It ends some time before the conclusion of the First World War later the same year. The third part of the trilogy, "The Ghost Road", continues the story. Whereas "Regeneration" is an anomalous, but not unique, mixture of fact and fiction,