White balance is one of those video functions that separates the weekend camcorder user from the more dedicated video maker. Casual users don’t understand this function, so their images often have an inappropriate orange or blue tint to them. The more experienced or interested users do care about this feature, and their images usually have more natural and life-like colours. So what is white balance?
As noted in a previous feature, all light sources are not white in colour. Each has a colour cast to it, and we refer to this colour as the light’s “colour temperature”.
Despite the use of the word “temperature”, the term has nothing to do with the actual light source’s temperature, but with the temperature of a reference material (a black metal) that was heated till it glowed. We use the temperature of this material (in degrees Kelvin) as a guide to how relatively “blue” or “orange” a light source is. The higher the colour temperature, the “bluer” (relatively speaking) the light is. The lower the colour temperature, the more orange the light is. Some examples are:
Light Source Colour Temp (K) Candle: 2,000 Sunlight at dawn 2,000 Tungsten-Halogen bulb 3,200 Morning/afternoon sun 4,400 Midday sun 5,500 HMIs (a type of arc light) 5,600-5,800 Midday sunlight plus skylight 6,500 Clear blue sky 10,000-20,000
Source: p.74 (extract) Brown, Blain. The Filmmaker’s Pocket Reference (1994) Focal Press
Remember, this colour temperature scale tells us nothing about a light source’s brightness or softness – only its colour.
Now that we know that outdoor light has a different colour to the light from indoor tungsten bulbs, we must compensate for this or our exterior shots will look blue and our interior ones orange. In short, white balance means “telling your camera what white is”, so that it can adjust its internal colour bias to correctly render the colours in the shot. Most video cameras offer three ways of achieving this:
1. Presets. Set the camera’s white balance to tungsten, and the light from most bulbs will now look white, giving natural colours under these shooting conditions. Or set it to daylight, and the light from the sun will look white and most footage shot outdoors during the day will look normal. But what if your light source is not quite one of these standards? Say, an unusually orange light source, or a really clear blue day?
2. Manual Setting. The other option is to hold something that you know is white (e.g. a piece of paper) immediately in front of the subject, zoom in on it, and then let the camera’s white balance circuits do the rest. This will give you a white balance that is uniquely set for your current shooting conditions, so that colours render more faithfully.
3. Automatic Setting. Either of the two options above is preferable to using your camera’s automatic white balance, which periodically adjusts the colour balance of the image to something approaching the right balance. This automatic feature is fine for casual home use, but if you want your footage to look professional you don’t want the colour balance changing during a shot.
So how come motion picture cameras don’t have a white balance function? Well, in a way they do. Motion picture camera film comes in two varieties – tungsten and daylight balanced. By using the appropriate film for the appropriate lighting situation, colours will be correctly rendered. If you are stuck with the wrong type of film, then corrective filters on the lens or gels on the lights can correct this (at the cost of absorbing some of the light).
The rolls of film you use for your stills camera are almost always daylight balanced. Daylight balance was chosen because most stills photos are taken either outdoors under daylight, or indoors using a flash – and the flash light is the same colour as daylight.
All of the above assumes, of course, that you want your light source to look neutral and white. If you don’t, then you can abuse the white balance feature to achieve other effects.
This may seem strange at first, but despite the fact that blue is a higher colour temperature than orange on the Kelvin scale, from an artistic or subjective point of view, orange is “warm” and blue is “cool”. There’s no real logical reason for this – it’s just an accepted stereotype.
By setting your video camera’s white balance to a slightly bluer source than what you are actually using (say, by pointing it at something you know to be slightly blue not white, and setting the white balance from there), your images will have a slight orange cast to them. This can help invoke feelings of warmth and comfort in the viewer (if it’s matched by the image and story, etc).
By doing the reverse, pointing the camera at something slightly orange to set the white balance, then your images will have a slight blue cast to them. This can make the image look cold and bleak.
Or you could try pointing the camera at something you know to be very orange or blue and letting the camera’s white balance function try to set itself to this colour. It probably won’t be able to, but the effect of its attempt on all the other colours in your images can be an unusual look which you might be able to use (but like all extreme effects, less is more, and often this kind of effect is best left ot postproduction).
There’s still a lot more to colour temperature and white balance (such as the pink/green colours given off by fluorescent lights), but for now, experiment with your video camera’s white balance – once you’ve realized the versatility of this function, you’ll never use auto-white balance again.
Originally written for About.com’s Filmmaking page.