Auto-Focus, Built-In flash, motorized winding, Automatic programmed exposure, all in one package.
1. Active Focus: This system is is the least expensive to implement. Basically, it uses a high frequence voice (sonar) or today typically an infrared beam to measure the distance to the subject and then focuses according to the correct settings for that distance. The movement of the lenses is done by an electric motor.
2. Passive Focus System:
This type of system employs mechanisms that detect contrast in the field of view. Passive focus works by the camera adjusting the lens until it detects that the highest level of contrast has been achieved. Some difficulties may appear if teh subject is not contrasty enough and there is less noticeable change from one part of a picture to the other.
Image Based Auto-Focusing is trying to find a solution using Artificial Intelligence to determine a problem for a photographer.