Many cameras are fitted with a rangefinder mechanism. This is used to focus the camera and adjust its ability to ‘see’. Over the course of a cameras lifetime, the internal mechanisms can shift and move due to everyday use. As a result the rangefinder will need to be adjusted in order to recalibrate the visual acuity of the camera.

In order to calibrate the settings of the rangefinder, the camera needs to be focused on something far away, (the moon works well). Then adjustments to the rangefinder are made until the images coincide.

In order to aid in focusing the rangefinder, a laser pointer can be used to point onto the wall, so that the camera can be focused against it. It will be necessary to know the exact distance to the focal plane, but this works well as the dot is small and coherent.