Camera lens points can be stretched what can not pull what is called what
Can not be stretched called "fixed focus lens", the focal length of the lens can not be changed, to change in the lens to see the object of the distance, it is necessary to rely on man step.
The lens is divided into two kinds,
Can be stretched called "zoom lens", stretching the action can change the focal length of the lens, that is, people do not have to move, you can change in the lens to see the object of the distance.
