Diaphragm (photography)
In photography, a diaphragm is a thin, opaque mechanical device having a generally adjustable central opening. It makes it possible to limit the number of rays of the light beam which arrive on the emulsion or the sensor. The diaphragm is centered on the optical axis and separates the anterior and posterior lens groups from the lens in which it is placed. In modern objects, it is most often a device of the iris diaphragm type constituted by a series of movable metal lamellae whose position is controlled by means of a ring placed outside the lens . The diaphragm setting can be manual or coupled to the camera body. The diaphragm has three main functions: ▪ regulation of the illumination of the sensor. ▪ changing the depth of field of the image. ▪ the limitation of the optical aberrations of the objective. It therefore has a decisive role in the clarity of the images produced. It is a regulator of the sharpness of the image.