Light sources vary from cool (blue coloured light) to very warm (bright orange coloured light). The automatic white balance (AWB) setting on an SLR evaluates the colour temperature of the light source that reaches the camera sensor and balances the RGB (red, green and blue) channels inside the camera to get the best result. AWB works fine for many types of light, especially outdoors.
However with some light sources one of the three RGB colours is dominant and the AWB setting canít balance it with the other two colours. This produces a colour cast in the final photograph.
For example, shade and overcast light have a slight blue cast, fluorescent light has a green cast, and Tungsten light and candlelight can have a yellow or orange cast. These types of light are most often found indoors. Flash also has the effect of making a photo appear too white and cold.
The colours in the frame can also affect the light and create colour casts. For example light reflected off a wall painted red will create a red cast. A good way to know if your white balance is not quite right is if the white tones in a scene appear yellow, blue-grey or pinkish.
Photographs with pure white light without any colour cast are usually a result of choosing the right white balance settings to suit the ambient light, whether inside or outside (and sometimes combining it with off-camera flash that adds extra light without being too bright).
There are a few settings that can be used to get better white balance:
a) Preset white balance modes (instead of Auto)
Selecting the daylight, cloudy, shade, fluorescent, Tungsten or flash white balance modes will set the colour temperature to counteract the colour cast.
These modes are best to use when you can see an obvious colour cast in your photograph when looking at it on the LCD screen.
b) Custom white balance
Check your camera manual about how to find your Custom White Balance setting. Once youíve found it you need to fill the frame with something white under the type of light you will be shooting in, and take a photo.
Then take a second photo (it doesnít matter what is in the frame for the second photo). This will set the Custom White Balance for any future photos you take and ensure the white balance is suitable for the ambient light you are working in at that time, no matter what type it is. Just donít forget to change it when you move to a location with different light.
Take a look at the photos below to see how each preset mode looks compared to Custom White Balance:
c) Shooting in RAW
Thereís more data available in a RAW file than a JPEG file which makes it easier to alter the colour temperature with editing software to get the correct white balance. Itís always a good idea to choose RAW format when youíre taking photographs in tricky light.