"How to focus properly?", "What does DOF mean?", "Is auto-focus precise?", "What does back-focus and front-focus mean"?

Focusing is not as easy as it could seem, but it's one of the most important technique in photography, since a dark or too bright photo can be corrected via software, while an out of focus photo very hardly if not at all.

This lesson presents the basic principles of focus that are useful to be known.

1) Focal Plane

The "Focal Plane" is an ideal plane perpendicular to the camera lens and at the distance where the lens is focusing.

Example: if you are pointing the lens towards horizontally and focusing at 3 meters of distance, the focal plane is a vertical surface in front of you at 3 meters of distance in focus (if the lens is perfect).