What's the depth of field and the bokeh and how to control them?

Picture with small depth of field and the bokeh — Picture showing a very small Depth of Field with the blurred bokeh

The Depth of Field (also called DoF) on a picture is the part of a picture which is in focus, the bokeh is everything else which is blurred, in fact the word bokeh come from Japan and mean the quality of the blur.

There is 4 factors to control the depth of field and the bokeh, and those four factors are tightly linked together

The aperture of the lens.
The focal length of the lens.
The distance to the subject.
The distance of the subject from the background (for the bokeh).
Optional: The size of the sensor if the lens is not meant for it (it's arguable).

So let's start by watching this excellent video, very well put and easy to understand, from Dylan Bennet called A simple guide to Depth of Field which is worth the 15mn, and i do not know someone after watching this, who still does not understand Depth of Field in photography.

below you can see the result of different depth of field at different focal length and different aperture.

Recommended after reading this page Focal length, wide angle telephoto and zoom.

You might also be interested with the last entry in the blog:

Photophone: How to do great pictures with a smartphone or a tablet.

Tue 25 Oct 2016

How to take great pictures with a smartphone?

Nowadays our smartphones have more computer power than a 10 years old desktop computer. Technology is evolving fast and with it, the language acquiring new words like smartphone or selfie.

We are doing everything with our phone, from a GPS assistant to photograph or record a movie in full 1080p HD, even post processing those images, and i don't even speak about playing 3D games, read some news on internet and so on...

At the end, when we compare how we use our phone the most, in percentage, I can say safely that we barely use it to call someone, and this is why i call mine a photophone.