What Everyone Should Know About DIAPHRAGM
Diaphragm is a hole in the center of a ring; it meant to control the amount of light entering the camera and to shut out all other extraneous light so that the photograph isn't overexposed.
The function of the diaphragm is to make sure that light only enters the camera’s lens through the aperture. We also call diaphragm “a stop” or “an aperture stop”. It consists of several overlapping metal leaves inside the lens that form a circular opening of variable sizes.
Diaphragm can be 1.4, 1.8, 2, 2.8, 4, 5.6, 8, 11, 16, 22, and 32. These numbers are called stop numbers or f-numbers. The squares of the f-numbers are inversely proportional to the amount of light admitted. In the above international standard series, each setting admits twice as much light as the next higher f-number (giving twice as much exposure).
If you have a reflex camera with demountable objective lens and a diaphragm ring you can see stop numbers on it and change it by turning a ring. If not, you have to go directly to the MENU of a camera and search for DIAPHRAGM (F)
The diaphragm 1.4 is the largest aperture and the diaphragm 32 is the smallest one. If the aperture is wide the image is brighter that is why the time of exposure isn’t big. If the aperture is small the image will be too dark that is why you have to enlarge the time of exposure. So if you chose the diaphragm with number 1.8, for example, it means that you need a lot of light to take a picture (it can be in the night or in the dark room).
One more aspect concerns image sharpness. We often have a situation when we want all objects to be sharp. For example, it concerns landscape. In this case we need to close our diaphragm (it’s better to use numbers 11, 16, 22, 32) and all our objects will be sharp wherever they are: distant or at short range.
On the opposite side if we need only one object to be sharp or just one very detail we should use a large aperture of the diaphragm. For example, if you want to make a portrait you may need a blurred background (use a diaphragm 1.4, 1.8, 2 or 2.8 to get this effect).
So if you want to use a diaphragm 1.8 or close to it you have to choose very carefully on what you want to focus because everything else will be blurred. Using this technique you can achieve different aims. You can photograph one object in different ways just using the focus:
So you should know in which conditions it’s better to set a small or a large aperture, for what you are going to use this or that diaphragm and how it can influence your photography.
If you want to share your experience you are welcome to our Photo Forum
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