White Balance for digital cameras
How to adjust the white balance on a television or video camera.
White balancing adjusts the camera so that it gives true colours for a given colour temperature.
Basic White Balancing
- Make sure the camera is not switched to "Preset" or "Auto White"
- Hold a white card (sometimes back of script or white tee shirt) in the ambient light source
- Point the camera at the white card so that it fills more than 70% of the frame
- Correctly adjust the exposure to give white in the viewfinder (if it's not exposed correctly you'll get an "over level" or "under level" message)
- Press the Auto White switch
- After a few seconds you should see a "White Balance OK" message
- Camera is now white balanced
Creative White Balancing
Some cameramen carry a selection of off white cards and use these to creatively manipulate the overall colour balance of a scene.
For example, if you carry out the basic procedure as described above, but use a slightly blue card instead of pure white, the camera will adjust to make this blue card appear white. In effect, it has adjusted to a cooler colour temperture than the actual light falling on the card. The overall effect of this is to make the scene appear warmer or more orange. Conversly, you can make the scene appear cooler or more blue by white balancing on a slighty orange card.
Balancing for mixed light
When a scene is lit with a mixture of different colour temperature sources, you have to make a decision on where to set your white balance. There is no right or wrong way of doing this as it is a subjective and creative decision which dictates how the scene will appear and can control the overall mood or look of a scene.
For example, you're filming inside a building that is lit with domestic tungsten lights and you have the windows in shot so you can also see outside. So, if you balance for tungsten light inside, white will appear white and flesh tones will be correct but the outside will appear blue. You can't colour correct all the tungsten lights with gel nor can you put colour correction gel across all the windows, (unless you're shooting a feature film of course) so you'll have to come to a compromise. This is generally no bad thing and most cameras now handle mixed colour temperatures very well so you can achieve a pleasing and accurate image.
It's probably best to set your colour balance somewhere between daylight (6300K) and tungsten (3200K) and one option is to use a preset of 4300K. This will make the interior slightly warmer and the exterior slightly cooler and this is generally desirable as we all percieve interiors to be "warmer" than exteriors. A "perfect" colour balance where all the light is uniform can lead to a flat an uninteresting image so it's often a good idea to retain some of the colour interest especially in "on location" scenes. The extent of the blue and orange tones will depend on the specific type of lights and the weather and time of day outside and indeed may be beyond what is acceptable to you. So, if the inside is more important to you, then you will err towards a colour balance closer to 3200K but the downside of this is that the outside will appear more blue. You can finely tune the colour balance by placing your white card in mixed light so that more tungsten falls on it than daylight or vice versa and keep trying white balances until you achieve an acceptable result.
If you can't achieve an acceptable mixed light balance, then you'll have to start colour correcting lamps, adding your own lighting or avoiding the windows.