Parallax in Photography is defined as the apparent change in position of an object when the photographer moves his own position along with his camera. Parallax is an optical phenomenon and it is important in taking distant photographs.
What is Parallax ?
Parallax is defined as the angle between two straight lines from different locations to the same point ( of an object). This is the angle subtended by the base line from the observed point.
If one pick up a pen and move it fast or alternately see it only with either the left and right eye, then its image moves from the more distant background. The angle at arms lengths on average about 6 degrees. The parallax is greater as closer the observed object and the longer the base line.
The barely conscious Parallax is present in everyday phenomenon which basically acts an indirect method for estimation of distances. By determining the parallax of a sensor or measuring telescope and when the baseline is known, the distance to the target point can be calculated exactly.
Parallax in Photography
Apart from the scientific and practical usage of the phenomenon of Parallax, Parallax in Photography. In the photograph Parallax occurs in all binocular cameras, both rangefinder cameras and twin-lens reflex cameras – the image in the viewfinder and the resulting photographic image do not match. This error is naturally greater as closer the object is. Simple cameras with with separate viewfinder often have an additional fixed mark for the short-range, more complex models have an automatic parallax correction : focusing the camera is not only to focus of the lens, but also it changes the angle between the viewfinder and the lens. Digital SLR cameras are from parallax errors the image of the viewfinder comes directly from the image sensor. Thus a more accurate image can be taken.