Camera
controls are interdependent. The total amount of light reaching the film plane
(the "exposure") changes with the duration of exposure, the aperture
of the lens, and the effective focal length of the lens (which in the variable
focal length, can force a change in the target opening that is zoomed).
Changing
these controls can alter the exposure. Many cameras can be configured
to meet most or all of these controls automatically. This automatic
functionality is useful for occasional photographers in many situations.The duration of exposure is considered the shutter speed, often even in cameras that do not have a physical component, and is usually measured in fractions of a second. It is quite possible to have an exposure of several seconds, usually still life subjects, and scenes of night exposure may be several hours.
The effective opening is expressed by an f number or f-stop-(opening ratio derivative), which is proportional to the ratio of the focal length and the diameter of the opening. The lens is less light, even if the diameter of the aperture is the same because of the greater distance the light has to travel: short lens (shorter focal length) is brighter in the same size opening.
The smallest F/ number, the opening is more effective the current number system to f the effective aperture of a lens has been standardized by an international convention. There were earlier, different sets of numbers in old cameras.
If the number decreases by a factor f of the diameter of the aperture is increased by the same factor, and its surface is increased by a factor of 2. Diaphragms can be found in a normal lens are 2.8, 4, 5.6, 8, 11, 16, 22, 32, who will "stop" (smaller f-stop) to twice the amount of light reaching the film, and a bottom stop to half the amount of light.
Image capture can be achieved by various combinations of shutter speed, aperture and film speed or sensor. Different (but related) of aperture and shutter speed for photographs taken under different conditions of film speed or sensor, lighting and movement of subjects and / or a camera, and desired depth of field. A slow film speeds are less "grain" and a slower speed the creation of an electronic sensor are less "noise", while most movies and speed sensors allow a faster shutter speed, which reduces blur movement or allow the use of a smaller aperture for increased depth of field. For example, a larger opening is used for less light and a lower opening more light. If an object is moving, and then a fast shutter speed may be necessary. A tripod can also be useful as it allows for a slower shutter speed to use.
For example, f / 8 to 8 ms (1/125 seconds) and 5.6 to 4 m (1/250 of a second), we obtain the same amount of light. The chosen combination has an impact on the outcome. The length of the opening and the length of the lens to determine the depth of field, which refers to the range of distances from the lens to be developed. A longer focal length or greater openness will lead to "shallow" depth of field (ie, only a small plane of the image is in sharp focus). This is often useful to isolate issues lower than in the individual portraits or macro photography. Conversely, a shorter lens, or a smaller opening will result in more of the image being developed. This is generally more desirable when shooting landscapes or groups of people. With very small openings such as holes, a wide range of distance can be selected, but the sharpness is considerably degraded by diffraction with small openings. In general, the greater degree of "sharpness" is an opening in its middle range of a lens (eg, f / 8 to a lens with openings available from 2.8 f/16). However, as technology improves lenses, contact lenses are becoming capable of making more vivid images with large openings.
Image capture is only part of the process of image formation. Little equipment, a process must be used for the latent image captured by the camera into a visible image.
