Diaphragm Control Exposure
Many of the people in the photographic circle take it to the analogy of the background. Little understanding of its other aspects, in fact, the aperture is only a physical image in optical imaging, and shutter speed and sensitivity together determine the camera exposure, as the aperture size caused by the background blur effect is different, it is one of the physical characteristics It is not simply control the background blur effect so simple. How is the aperture used by photographers? Let's talk about it.
Aperture is used in the camera lens to control the amount of light through the device. A lens produced, the focal length, lens diameter, like the field are often fixed, and this time if we want to control the camera through the lens to receive the size of the light, you need to let the light through a device, through the lens can be adjusted size The hole grating controls the amount of light received by the camera. This device is the aperture.
And we usually use the camera, set the aperture value, set the aperture value F, F value to determine the size of the use of the aperture when the camera, but the aperture and the physical aperture size is not directly related to the aperture value of F is: F = the focal length of the lens / the diameter of the lens aperture, meaning that the aperture value F is determined by the focal length and the physical aperture of the aperture.
We often say that the large aperture lens, is indeed the largest physical aperture larger lens, but never directly labeled aperture size, but with the F value to mark. From the formula we can also see that a lens focal length fixed case, the aperture value and the lens aperture diameter is inversely proportional to, so there is a smaller F value of the larger aperture of the conclusion.
The role of the aperture
The biggest effect of the aperture is to control the exposure, different maximum aperture value of the lens because the price difference is huge, because the maximum aperture adjustable range is much larger than the largest aperture. Unlike the shutter speed adjustment exposure, the range of the aperture control exposure is physically determined by the device and can not be determined by the time of the shutter speed. Therefore, the control range of the aperture is large, mainly the inherent specification of the lens, that is, Decided by the wallet.
For photographers, the advantage of large aperture control exposure is more important than the output background blur effect. This should start from the film era. Today we use a digital camera, the exposure by the aperture, shutter, ISO to decide. The film age is also determined by these three parameters, but ISO is determined by the sensitivity of the film, which means that when you insert a roll of film, before the film is finished, you can not adjust the sensitivity, exposure The amount is determined by both the aperture and the shutter. In order to keep the shutter speed in the range does not affect the hand, then the lens requires a large enough aperture.
Aperture greater than F1 lens is rare today, only a few lens manufacturers test the water. But in the film era there are many manufacturers have introduced F0.95 such products, in that hardware crazy refresh the inside, a lot of God-level specifications of the wonderful product launch market, the reason is the film sensitivity limit, must continue to brush High hardware specifications to make up for the inconvenience of use. So although the F0.95 lens in the maximum aperture when the resolution is very low, is still very popular with the photographer, you can solve the problem of shaking in low light.