Diaphragm

A Diaphragm is a round device on the face of the camera that has an opening at its end known as the “aperture“. The function of the diaphragm is to make sure that light only enters the camera’s lensthrough the aperture. While the aperture can be widened or narrowed to allow more or less light into the camera, the diaphragm is meant to shut out all other extraneous light so that the film isn’t overexposed.

Because it limits the passage of light, a diaphragm is also known occasionally as a stop or an aperture stop. Adjustable diaphragms are called iris diaphragms or merely irises.

A comparable analogy for the way a diaphragm and aperture works can be found in the human eye. While the eye’s pupil allows light to enter the eye (like a camera’s aperture), the iris blocks the entrance of light (like the diaphragm).

An alternative to the iris diaphragm is a diaphragm that consists of a series of “blades.” This more primitive type of diaphragm was more prevalent in older camera models. The more blades available on these older diaphragms, the blurrier the pictures of the images will be.