How a Camera Works
A camera works through a series of reflections, the basic technology that makes it possible is very simple. A still film camera is made of three basic elements: an optical element (the lens), a chemical element (the film) and a mechanical element (the camera body itself).
The optical component of the camera is the lens. At its simplest, a lens is just a curved piece of glass or plastic. Its job is to take the beams of light bouncing off of an object and redirect them so they come together to form a real image – an image that looks just like the scene in front of the lens. As light travels from one medium to another, it changes speed. Light travels more quickly through air than it does through glass, so a lens slows it down.
When light waves enter a piece of glass at an angle, one part of the wave will reach the glass before another and so will start slowing down first. The effect on light is the same; as it enters the glass at an angle, it bends in one direction. It bends again when it exits the glass because parts of the light wave enter the air and speed up before other parts of the wave. In a standard converging, or convex lens, one or both sides of the glass curves out. This means rays of light passing through will bend toward the center of the lens on entry.
This effectively reverses the path of light from an object. A light source, say a candle, emits light in all directions. The rays of light all start at the same point (the candle’s flame) and then are constantly diverging. A converging lens takes those rays and redirects them so they are all converging back to one point. At the point where the rays converge, you get a real image of the candle ie the flame. The rays enter through the shutter and pass the aperture.
The chemical component of the camera is the film. In film cameras, there are chemicals in the film that change their nature when exposed to light. The silver salts that the film is made up of react and darken, the more light that hits the film the darker it gets. The film is forming a negative image. The darker something is on your negative the lighter it will be on your print. These chemicals are on such tiny grains that you would have to blow up the picture many times to see the “graininess”.
The camera body itself is the final component in looking at how the camera works. In conjunction with the lens which filters light and the film which is altered when exposed to the light, the camera has many functions which make it all possible.
1. The Shutter release button which opens the shutter to let the light in. The longer the shutter stays open, the more light
comes in. This is called the shutter speed.
2. The aperture, or the size of the hole in the camera, is also important this determines how much light comes in. Both the
shutter speed and the aperture control the amount of light that strikes the film. This is known as exposure.
3. When you look through the viewfinder at the back of the camera you will see almost what your photograph will look like.
4. The focus measures how far the subject is from the camera and determines the clarity of the subject.
5. Some cameras have a Flash unit, when it is dark, the camera determines if you will need extra light . Some cameras will
do this automatically and others will require you to turn the flash on. You can now take a picture in low light. When you
take your photograph, a light will flash.
6. The spool within the camera is what the film winds around after each shot has been taken, this prevents double exposure
from occuring.
7. Opposite to the spool is the film chamber which holds the film canister in place.
Your Task
In your books draw the diagram above of what a standard camera does when projecting an image onto film. Once drawn give a brief description of what is happening in this diagram to help you understand what you have read above.
