PURPOSE: To demonstrate depth of field as a function of aperture setting, and to demonstrate field of view as a function of zoom setting on a TV lens.

DESCRIPTION: (1) Depth of field: Open the lens aperture with the Fresnel spotlight off, set the camera to full zoom (100), and place the camera at the closest distance at which it is possible to focus on the nearest can. Focus on the middle can, and observe the focusing of the extreme cans (photograph at right). Then turn on the spotlight so that it illuminates all of the cans and close the f-stop so that the lighting level is the same as before. Observe that the depth of field increases, because the increase in light level allows use of a smaller aperture (photograph at left).

Field of view: Vary the zoom and observe the change in the size of the field of view.

SUGGESTIONS: This works best with an old black and white camera which you can control directly, but also works using a color minicam under correct conditions.

REFERENCES: (PIRA unknown.)

EQUIPMENT: Six soda cans, minicxam with manual focus, (black and white TV camera with 12.5-75mm zoom is alternate), Fresnel spotlight.

SETUP TIME: 5 min.