Motor usage in the lens of cameras is illustrated on this slide. For auto focus, a stepper motor is used. This application requires two lenses, as the figures in the upper right image show. There is a main lens and the focusing lens. By adjusting the position of this lens, the object will come into focus. This requires precision, therefore a 3 to 5 V stepper motor is used. Zoom does not require the precision in position control that focus does, so often a brush motor is used. The lens iris controls how much light gets to the image sensor. A motor is used to make this opening larger or smaller. A stepper or brush motor is used to position the blades that control the size of the opening.