A lot of fuss is made over exposure and it can get really complicated. No more read on!
Put bluntly, exposure is just the right combination of factors needed to make a decent image. A correctly exposed image needs just the right amount of light to fall on the sensor.
The amount of light falling on the sensor is determined by the shutter speed and the aperture.
The shutter speed can be seen as the amount of time the sensor is exposed to light (the faster the shutter speed the less light falls on the sensor). The aperture can be seen as the amount of light that can be let in through the lens (the bigger the aperture the more light comes in).
In average conditions, the faster the shutter speed the bigger the aperture that is needed to let light in. Conversely, the slower the shutter speed the smaller the aperture needs to be.
You can put this the other way around for a big aperture you need a fast shutter speed and for a small aperture you need a slow shutter speed,.
If too much light comes in the image is overexposed whited out. If too little light comes in then the image is very dark.
Dont worry your camera will do all this work for you if you put it on automatic mode (program mode). But sometimes the camera will be fooled into giving the wrong exposure (especially in very bright or very dark condition). In this case you can override the exposure by using aperture priority, shutter priority or manual mode. Check your camera instruction manual for further details and experiment.
Eric Hartwell runs the photography resource site http://www.theshutter.co.uk and the associated discussion forums as well as the regular weblog at http://thephotographysite.blogspot.com
