A 35mm lens set to f/8; the diameter of the heptagonal diaphragm opening is 4.375mm

In optics, a diaphragm is an opening in the lightpath of a lens or objective that can regulate the amount of light that passes. The centre of the diaphragm coincides with the optical axis of the lens system. Normally it is shaped in a near-round fashion by a number of curved blades. Diaphragms usually have five to eight blades, depending on the intended uses, pricing and quality of the device in which it is used. Furthermore, each blade can be curved, resulting in an 'inflated' pentagon (or octagon) shape, to improve the overall roundness of the iris opening. Download high resolution version (1200x1200, 524 KB) Wikipedia does not have an article with this exact name. ... Download high resolution version (1200x1200, 524 KB) Wikipedia does not have an article with this exact name. ... A 35mm lens set to f/11, as indicated by the white dot above the f-stop scale on the aperture ring In photography the f-number (focal ratio) expresses the diameter of the diaphragm aperture in terms of the effective focal length of the lens. ... In geometry, a heptagon is a polygon with seven sides and seven angles. ... See also: List of optical topics Optics (appearance or look in ancient Greek) is a branch of physics that describes the behavior and properties of light and the interaction of light with matter. ... A lens. ... Photographic lens The zoom lens of the Canon Elph A photographic lens (or more correctly, objective) is an optical lens used in conjunction with a camera body and mechanism to make images of objects either on photographic film or on other media capable of storing an image chemically or electronically. ... In telecommunication, the term optical axis has the following meanings: 1. ... In geometry, a pentagon is any five-sided polygon. ... One of the 8 semi-regular tessellations: octagons and squares An octagon is a polygon that has eight sides. ...

Many cameras have an adjustable diaphragm to control the amount of light, which can also be regulated by adjusting the shutter time. The principle is identical to that of the iris in the human eye. A camera is a device used to take pictures (usually photographs), either singly or in sequence, with or without sound recording, such as with video cameras. ... The shutter speed dial of a Fujica STX-1. ... The human iris The iris is the grey-brown area. ...

A small diaphragm reduces the amount of light, but also reduces the influence of aberrations of the optical lens system and increases the depth of field. The reduced light intensity will however require the shutter time to be increased, which leads to increased blurring if the subject of the photograph or the camera moves during the exposure. This article needs to be cleaned up to conform to a higher standard of quality. ... An example of very shallow depth of field in a macro photograph. ...

The number of blades in a diaphragm has a direct relation with the appearance of the blurred out-of-focus areas in an image, also called Bokeh. The more blades a diaphragm has, the rounder and less polygon-shaped the opening will be. This results in softer and more gradually blurred out-of-focus areas. The astounding bokeh of a Helios-40 lens A photograph of jonquil flowers with background bokeh Compare a photograph of jonquil flowers with low background bokeh Bokeh (from the Japanese boke ぼけ, blur) is a photographic term describing the subjective aesthetic qualities of out-of-focus areas in an...

In a picture, the number of blades the diaphragm used has, can be guessed by counting the number of spikes converging from a light source or bright reflection. There are always twice as many spikes as there are blades.

In case of an even number of blades, these spikes will overlap each other, so the number of spikes visible will be the number of spikes in the diaphragm used. This is most apparent in pictures taken in the dark with small bright spots, for example nightly cityscapes.

See also

• Aperture