Depth of field. Definition.
What is the depth of field ? Simply, it is the clearness present before and after the subject on which we focus. (That is to say the space between the nearest and furthest clear points.
Depth of field. Use.
By increasing the depth of field, subjects will be clearer in a larger distance. The picture of the tree is clear not only near but also further. The depth of field is at its maximum.
A large depth of field can be useful to focus on manyfold distant objects. Conversely, with a shallow depth of field you will obtain an unclear background or a clear foreground. This shallow depth of field will ’delete’ the plans before and after the object. This picture of insect is a perfect example. [1]. The last plan blurred didn’t have much importance.
The depth of the field always expands itself more in the background than in the foreground. For portraitures, the distribution is about a third in the foreground and two thirds in the background. For landscapes, and if the clearty goes infinite, the background is infinitely wider than the foreground. In micro photography, the depth of field is divided in two equal parts. An automatic camera could guarantee an high performance set.
How to reduce or to increase the depth of field.
You will increase the depth of field by closing the diaphragm of the camera. Conversely, by opening it, you will obtain a shallow depth of field and will only focus on the object.
To understand, some practise is needed :
Hanging to your camera, you look at the numbers that match to your diaphragm. They 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... The bigger the numbers get, the wider will be the depth of field, the smaller they will be, the shallower...
Depth of field on digital camera.
By using your camera with a manual mode, it is possible to set the depth of field. Semi-automatic modes can also give you an high performance photograph : with a good camera you can adjust the priorities or the modes P.A.S.M.
– The aperture priority or ’A’ : With the control on opening/closing the diaphragm, it is possible to adjust the depth of field. Smallest figures (large apertures of the diaphragm) offer a shallow depth of field.
Read also : Speed and diaphragm
