This tutorial is a guide to help you make the most of some of those features.
• Understanding exposure
• Metering modes
• Exposure compensation
• Auto Exposure Lock (AEL)
• Shooting modes
When you take a photograph, a sensor inside your camera is exposed to light. There are three elements to this exposure – the brightness of the light, the length of time it is allowed to act on the sensor and the sensitivity of the sensor.
The lens aperture controls the brightness of the light. It opens or closes to let more, or less, light through to the sensor. The duration of the exposure is controlled by the length of time the shutter is open (the shutter speed).
The sensitivity of the sensor is controlled by the ISO setting. Whilst an ISO value of 100 has negligible amplification, the amplification at higher ISO settings makes it possible to obtain images in very low light.
This might make you think the best ISO setting is the highest one. But one of the effects of increasing the ISO is an increase in ‘noise’ – coloured specks that start to appear in the images. So, in very low light, exposure can be a compromise between detail and noise.
Current EOS cameras operate within a very wide ISO range; the first step into the DSLR world, the EOS 1100D, works with ISO settings of 100 – 6400, whilst the professional EOS-1D Mark IV can be expanded to 102,400.