Depth of Field traditionally belongs to optics and has been under photography for many years. Depth of Field is the area in which the image captured by the lens is sharp (that is, it is focused), so that in the photograph is, people and objects that are within that area also appear sharp. A more complete and accurate definition of Depth of Field would be: Depth of Field is the space in front and behind the plane of focus, between the first and last points which are clearly reproduced in the same plane of focus.
Factors influencing Depth of Field
Depth of Field depends on four factors :
- Size of the circle of confusion and therefore the format and size of print
- Distance of object
- Focal length
- f Number
Depth of field thus depends on the focal length. It has been said earlier that the focal length does not vary, so the depth of field will not vary. Instead of observing in this way, we actually observe from a distance proportional to the size of the object – it turns out to be the most influential parameter is the depth of field. This difference increases when we look at the same distance, since this is only influences the focal distance.
There is no Depth of Field in real life
Depth of Field only exists in the context of reproduction. It is an intrinsic property of a lens and depends on subjective appraisal values. Depth of Field refers to acceptably clear the area around the plane of the image is in focus. All points in a picture are out of focus to some extent although might not be obvious, only one plane is perfectly focused. Depth of Field limits preciseness where the lack of sharpness becomes unacceptable to the observer.
Imagine the box created by the yellowish lines is a cut out and the blue lines are a part of a virtual paper curving towards outside.
Depth of Field increases inversely with aperture, that is, the more it is closed or larger the f number is chosen it Depth of Field will increase. For example, with an aperture of f5, Depth of Field will not be very large, while an aperture of f16 Depth of Field will be considerable.
On the other hand, the closer you are to the object you want to photograph – the lower is the depth of field, regardless of the selected aperture. Telephoto lenses also reduces the depth of field. But with wide angle lenses, depth of field increases.