Part 4 - Light

The meaning of the word photography comes from the greek word phos, photos - light and graphos - writing. Painting with light is often an expression photographers use. The very essence of photography is light, without it we don't have an image. 'Photography is the manipulation of light' (Light, science and magic, page 13). Therefore if can control the quality of the light we are well on the way to making a successful image. 

How do we measure the light?

All modern DSLR's have a selection of different metering modes. They all work to assist the photographer in obtaining the best exposure for whatever scene you are presented with. I have been using various models of Nikon cameras over the years, I currently use a D4 and D300. 

Nikon use three different metering modes:

Matrix - with this setting the camera meters a wide area of the frame and sets the exposure accordingly in relation to the distribution of brightness, colour, distance and composition.  

Centre weighted - Camera meters the entire frame but assigns greatest weight to the area in the centre 8mm of the frame within the viewfinder. 

Spot - Camera meters a circle of 3mm (approximately 2% of the frame) The circle is centred on the current focus point, making it possible to meter off centre subjects. 





The principle of metered exposure is that the area being measured are averaged and the exposure set via the shutter speed and aperture so that the result is a mid tone, or in other words half way between black and white. 

These metering methods work well on most occasions but when faced with situations in which the results may be lighter or darker than you expect there are two ways of altering the exposure. One is to switch the camera's metering from auto to manual, and the other is to use exposure compensation. The former is my preferred method.