Although its perfectly possible to take good photographs without understanding the
camera having an idea of what happens inside the box really helps.
The Basics
Ultimately the workings of film and digital cameras are the same. Both types
function by controlling the light as it enters the camera to produce an image on
the film/sensor. There are three ways that the camera controlls the light
-
- The lens - often there's actually more than one physical
lens (often referred to as
elements) within the lens on a camera. This focuses the light to give a sharp
picture
- The aperture - an adjustable opening to control the total amount of light entering
the camera
- The shutter speed - the shutter opens to let the light in when you take a picture,
the time it stays open can be altered
Exposure
The aperture and shutter speed combine to control the amount of light entering the
camera. Depending on how bright the subject you're photographing is and how
sensitive the film/sensor it (see below) a certain amount of light is needed to
produce a picture which is correctly exposed.
If the aparture is wide open, much light can enter the camera. To stop too
much light coming in and over-exposing the picture (which would make it too light)
a fast shutter speed would be needed (i.e. a short delay between opening and closing
the shutter).
If the aperture is closed right down to restrict the light getting in as much as
possible, a slower shutter will be required else the image will be under-exposed
(too dark).
Traditionally a light meter is used to measure the light coming from the subject
and work out the amount required in the camera to give a correctly exposed image.
Modern camera have metering built in and can work out the aparture and shutter speed for
you.
Taking a Picture
When taking a picture with a compact camera, the camera makes the desicions on what
aparture and shutter speed to use to get the correct exposure and adjusts the lens
to bring the image into sharp focus (autofocus). The light passes through
the camera as shown in the diagram below.
The mirror in the diagram is only usually found in an SLR camera (Single Lens Reflexive)
where it is used to bounce light up to the viewfinder so that you see precisely
what is coming in through the lens. Many compact cameras either have a window
viewfinder to look through which shows you roughly the same as what is coming in
through the lens, or they rely on an LCD display to show you what the camera is
seeing.
With an SLR camera all of the factors listed above (and a good many more) can be
altered manually. This gives SLR users much for 'creative control'.
By this I mean that you can better control how the image will look. Read on
to find out why...
Read more about the
Aparture
Read more about the shutter
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