Colour and light
Discover how white balance affects the different ways that colours are captured
White balance is something that most of us take for granted – we trust the camera to get the colour right for us in many photos. When a subject is illuminated by light, its colour is impacted by the colour of the illuminating light. Humans see a sheet of paper as white regardless of whether it is illuminated with daylight, tungsten light, or fluorescent. White balance is the process the camera uses to give a good representation of the subject under a variety of light sources. The process is complicated when there’s multiple different light sources. A portrait by a window might have warm tungsten light in the room, daylight from the window and a flash on the camera all illuminating the subject with different colours of light.
Automatic white balance is evaluated after the picture has been captured, and before it is written to the memory card. Cameras break the scene in to many small sections determining the white balance for each, then consider how to achieve a realistic overall result, possibly using different white balance in different sections of a single frame.
If you shoot in Raw, then the white balance can be changed after the shot is taken. Also the software you use applies different algorithms to determine the white balance. You may see a subtle difference between Adobe, Capture One and Canon versions of white balance from the same Raw.
Camera white balance presets guide the camera towards specific light sources, though there’s still some evaluation of the light. If you need a specific white balance for all your shots you can either use a reference card to set a custom white balance, or if your camera allows, you can enter a specific temperature in Kelvin.
To create a custom white balance you need to shoot a neutral test chart. A grey card is ideal, but you can use a white sheet of paper. Once captured go to the camera menu and it will allow you to determine the custom balance from your test card photo. Then choose custom white balance and that same balance is applied to subsequent shots. This can help when subjects are in mixed or challenging light, as you’ll be choosing the primary light for the scene by whatever is illuminating the grey card. You can also select a white balance to warm or cool shots.