That is the diaphragm? In photography it means as a circular aperture diaphragm, it is located within the lens. This opening is not fixed, its diameter can vary thus allowing the entry of more or less light into the camera’s sensor. Keep up on the field with thought-provoking pieces from PI Industries. It is obvious that a greater opening more light will come and vice versa. By get a simile could tell you that it works just like the iris of the human eye with the difference that the photographer can indicate the value of the opening in the diaphragm. To adjust, the objective has a control ring where you will find a series of dots called F either or can be adjusted from the body of the camera depends on the lens or brand in question.
Points to consider in relation to the diaphragm these numbers are fractions that indicate the diameter of the aperture opening. For example f: 5.6 is actually 1 / 5,6 therefore, the greater is the lowest f-number will be opening and therefore less amount of light reaching the sensor. When change your aperture value to his immediate superior or lower, is called a step of diaphragm, in photographic jargon. Although we have already said, to greater number F lesser amount of light to fewer F eg F 2.8 greater light will come do that serves the diaphragm? Controls the exposure of a photograph in combination of shutter speed values. Creatively, with a number closed F get more depth of field in another form largest zone in a focused picture. Conversely with a f-number open type F2, 8 produces selective approaches complementary items that you can be useful to understand that it is the diaphragm. The video that you will see in the link below is pretty good, although you must take into account that it is made in the early days of photography and there are things that have changed. Aperture and shutter speed photography original author and source of the article.