Taking Photos...Camera Anatomy

Its easy enough to pick up a digital camera and quickly snap away but do we really understand how the basics of a camera work. The process of taking a picture involves refracting light through a lens but how does it all work. The article below was the best I could find in explaining it in its full detail.

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.

But how can a piece of glass do this? The process is actually very simple. 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. This is something like pushing a shopping cart from pavement to grass, at an angle. The right wheel hits the grass first and so slows down while the left wheel is still on the pavement. Because the left wheel is briefly moving more quickly than the right wheel, the shopping cart turns to the right as it moves onto the grass.

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. In a double convex lens, such as a magnifying glass, the light will bend when it exits as well as when it enters. 

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. In the next couple of sections, we'll look at some of the variables that determine how this real image is formed.­