Let's first take a brief look at what is the exposure. The exhibition is actually a combination of different possible combinations of diaphragm, shutter speed and the film sensitivity. These combinations determine how the prospective photo will look like - light or dark, diffuse or sharp, etc.

Shutter speed


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This is the parameter of time interval in which the shutter is open for receiving the required quantity of light (if the value is shorter, then you get the less light, if it’s longer - more light), that falls on the elements capturing the image.
The shutter speed measured in milliseconds and seconds (of course it lasted for hours in the past). The shutter speed determines the sharpness of moving objects. Let’s take flowing water as an object of shooting. If we make a photo at slow shutter speeds from 1/60 and slower, the water will be a little diffuse. On photos made on 1/250 and higher shutter speed the water will be almost still, depending on its speed of flowing.

Examples of different shutter speed

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Diaphragm

Diaphragm is the parameter of the lens opening size. It adjusts the intensity of the light flow on a photosensitive element. Due to this it is possible to regulate the smoothness of picture (the depth of sharpness in other words).
The diaphragm size varies from f/1.4 to f/22. The lowest value shows that the diaphragm is fully open (passes the maximum quantity of light for a particular lens) and the highest value shows the opposite.
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Another major advantage of the changing diaphragm is the depth of sharpness. For example if you want to take a picture and separate the subject from the main background, you should set the least diaphragm size of f/1.4. And if the subject and the background on the picture must be sharp, you should use the highest size f/22. See the example in the picture.
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Open diaphragm setting is very convenient when you need to hide some picture elements from the viewer or when you need to make photos in low lighting. The diaphragm with the maximum size is good for shooting a city or landscape, as it allows showing all the smallest details. It is also often used in advertising shooting.