Depth of Field

What is the depth of field? It is a simply sharpness distance before and after the subject on which we focus. (Either the space between nearest and farthest point).
By increasing the depth of field, subjects will net a great distance. The picture below has a maximum depth of field.



A large depth of field can be useful to review many shots away from each other. In contrast, shallow depth of field can ensure a blur background or foreground of the subject to photograph. Example with this picture below.
In portrait studio, the distribution is close to a third forward and two-thirds back. On a landscape when the sharpness extends to infinity, the rear area is much larger than the area before. In macro-photography, depth of field is divided half in front and rear. An automated camera should be able to provide a setting optimized.

How to reduce or increase the depth of field ?
By closing the diaphragm of the camera, depth of field will increase. On the contrary, in full aperture, depth of field will be very short..
To remember in practice:
Camera in hand, you look at the numbers that correspond to your diaphragma.
These can be: f: 1.2, f: 1.4, f: 2, f: 2.8, f: 4, f: 4.5, f: 5.6, f: 6.3, f: 7.1, f: 8, f: 9, f: 10, f: 11, f: 13, f: 14, f: 16, f: 18, f: 22 ... Over these figures are, the greater depth of field will be extended ... and conversely the more these figures will be smaller, the depth of field will be short.

Depth of field on a digital.
In sloppy automation of the digital camera, you can adjust the depth of field. A good device to adjust the priorities to diaphragma mode ( Aperture mode ) : A. The control on the opening / closing of the diaphragm to adjust the depth of field.
Smaller numbers (large aperture) offer a small depth of field, vice versa.