Play with depth of field
A few words and advices concerning this photographic and cinematographic particularity what is the depth of field. What is it about ? How to settle it? What "semantic" effect does this produce?
Photography, video and depth of field
Depth of field definition
The depth of field of an image, fixed or animated, is the area of the image that is clear. This can range from a few centimeters to infinity. On an image with very shallow depth of field the net area will be very short, conversely a photo or video with a very large depth of field will be clear over its entire extent.
Many online tools allow you to calculate the depth of field. On the internet this site http://35mm-compact.com/photographie/calculateur-profondeur-de-champ.htm and on mobile this app https://play.google.com/store/apps/details?id=in.zendroid.hyperfocal&hl=fr
Adjust the depth of field
On a conventional camera, two main factors control the depth of field:
- The diaphragm: the opening of the diaphragm is controlled by putting itself in "AV" mode. The lower the value, the sharper the area of sharpness will be. For example if you select f4 or better f2 you will have a range of sharpness of for example 3 meters whereas by selecting f8 or f16 you will have a sharpness range of several hundred meters or more depending on the focus distance chosen .
- The focal length and the focus distance: overall, the larger the zoom (100 mm for example) the sharper the area of sharpness will be, on the contrary by putting itself in wide angle position (24mm, for example) you will increase the sharpness area. This at digital sensor size and focus distance equal ...
More and more images are made using our smartphones for results often bluffing. Many models now have a function to reproduce this effect of shallow depth of field. The option is often activated by clicking a photo diaphragm symbol.
The principle, very often is that the smartphone makes two pictures with two different lenses, one blurred and the other clear, and superimposes them by adjusting the sharpness area. It is then possible after making the photo to accentuate or reduce the effect of shallow depth of field ...
Many other technical factors are involved in adjusting the diaphragm. It interferes directly with the shutter speed, which can also be partly controlled by digital or optical filters called ND. Perhaps the subject of another article on this blog ...
Why play with the depth of field and what effects does it produce?
- This allows to stagger your image, to put forward, in the axis of the depth, a plan compared to the others. Choosing a small area of sharpness will strengthen its purpose while putting the net area in context. For example, a face in a crowd, an object in its environment. Conversely to be a little off, against foot, it is possible to put the central subject blur and its net environment.
- Aesthetically, foreground blurs and backgrounds often produce (depending on the characteristics of your lenses) beautiful, bright gradients known as Bokeh. This creates an artistic atmosphere more and more used in cinema and even in TV reportage since the generalization of the use of DSLRs as shooting tools.
Images illustrating the effects of the opening of the diaphragm realized at the market of the Liberation and in the old Nice
We had co-authored a photo learning book a few years ago called "The agenda of the apprentice photographer" and still consulting for example at the library of Nice Louis Nucera, you will find many other infos about depth of field in photo. In the end to progress, nothing better than to visit the photo exhibitions as for example Abbott or Depardon in Nice.