Lenses are clear, rounded pieces of glass or plastic that bend light to form pictures. Cameras that are used to make moves can use a variety of different lenses. Cinematographers must know how to pick the right lens to get just the effect they want when they shoot a scene. Different lenses are used for wide shots, medium shots, and close ups. This activity shows how geometry determines which lens does what.
Cameras use a lens to collect light and make a picture on the surface of the film.
The lens bends light rays so that all the light from one point on an object in a scene comes together at a corresponding point on the film. For this to happen, the distance between the lens and the object and the distance between the lens and the film must be just right. You can see this happen by holding a magnifying lens over a sheet of white paper on your desk and slowly moving the lens up and down. If you change the distance between the lens and the paper, the picture, or image, will become blurry and then disappear. Measure the distance in millimeters between the lens and the paper when the image is sharpest, or in focus.