addition to the maximum brightness value indicated on the lens, we discover that our camera can operate on several other increasing values. That is, the diaphragm can be closed gradually to reduce the light reaching the sensor. The opening and closing movement of the diaphragm are automatically created when the camera calculates the correct exposure and goes hand in hand with the calculation of the exposure time, which is also automatic. Theoretically possible values \u200b\u200bare 1, 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32, 45, 64.
In practice, most of the cameras on the market value does not exceed 16 and, in the case of digital is around 8. This means that the objectives of these cameras can not restrict the diaphragm and so much more than offering a small range of possible values \u200b\u200bcompared to their cousins \u200b\u200bor analog to digital SLR cameras, which assemble professional goals.
What does it mean? That under conditions of bright sunshine the goal will not be able to close enough to filter the outer glow and the machine will dramatically reduce the shutter speed, which also can be done since, in particular, comes at a speed of 1 / 4000 of a second. So, given that still managed to produce a proper exposure, why should we bother to know the aperture and its values? The fact is that although the exposure is correct, however, the result will be very different depending on whether you shoot with an aperture of f2.8 and a time of 1 / 250 of a second, or with an aperture of f8 and a time of 1 / 30. The amount of light that passes will be exactly the same and therefore the exposure will be correct in both cases, however, the focus of the objects will not be the same. In fact, a lens with wide aperture will tend to limit the focus on the subject, blurring what is around him and a target iris will also burn very close objects that are close to us and further away from the subject. The extension of the ability to focus is called "depth of field." The broader, the better the chance to see all objects in focus in the image, regardless of their distance from the target and a point which we have centered the focus of our recovery.
In sports photography, you may need to manually control the shutter speed abandoning the fully automatic mode to switch to a semi-automatic mode where the work is set by the desired time and let the camera calculate the opening correct. This mode is called shutter priority and is usually identified by the letter S (shutter priority) in the programmable cameras. There is also a way of working with each other, which is set by hand in the aperture and let the camera automatically calculates the exposure time. This mode is called aperture priority and is strongly marked by A (aperture priority)
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