Some people mistakenly think all you need to do is find a scrap of white paper or card, put the card in front of the camera and press the button marked "White Balance".
Well, there's more to it than that if you want to have complete control over the video you shoot.
What is white balance?
White balance is a camera control that adjusts the camera's color sensitivity to match the prevailing color of outdoor light (cooler), indoor light (warmer) or fluorescent light (greener). On most cameras, white balance may be set either automatically or manually. On professional cameras, white balance can be set to match exactly the light source you're shooting with.
Auto White Balance:
Many cameras allow completely "automated" white balance. Amateur camera operators are fooled into thinking you don't have to worry about whether you're shooting indoors or out, the camera makes the color decisions for you when this setting is engaged. While auto white balance is convenient it's also prone to color shifts, especially under mixed light sources. For best results, professionals always perform a manual white balance anytime lighting conditions change.
Manual White Balance:
Manual white balance is a setting that allows camera operators to match the exact lighting used. It is the professional way to shoot and is very easy to accomplish. The operator generally shoots a "white card" and presses a white balance button that adjusts the red, green and blue CCD signals so that the white card appears "white" and exhibits no color cast. This procedure, of course, must be performed every time you encounter different lighting conditions. All professional cameras allow you set a white balance manually.
To determine what is "white", the electronics in your camera must be shown a white object under the light that you will be shooting in. This is called "white balancing" your camera, and you must do a white balance every time lighting conditions change.
It is especially important to re-white balance when moving between indoors and outdoors, and between rooms lit by different kinds of lights. During early morning and late evening, the daylight changes quickly and significantly. Although your eyes don't always notice, your camera will.
What is Color Temperature?
Each type of light has a numerical temperature, here are the (rough) temperatures of typical lighting conditions:
Fluorescent 5500K - 4000K
Incandescent (tungsten) 3500K - 3000K
The human eye/brain automatically compensates for the color temperature of light falling on an object. When you move from the bright, blue-tinted sunlight to the dim, yellow-tinted indoor lighting, your eye automatically adjusts to the different color of light and changes your perception accordingly. Unfortunately, even the most expensive video cameras can't automatically do what the eye does, so we have to show our cameras what we want them to read as "white" in any given scene. It is imperative that you white balance manually for the absolute best results.
The Importance of White Balancing: No single shot stands alone.
In any given location, and within a sequence of shots, or scene, you must strive to maintain consistency with your white balance. Knowing how often to white balance is mostly a matter of experience.
Of course, if your camera white-balanced perfectly, the color balance of all your footage would be the same and the result would be very boring. A standard white balance will almost always make your footage look like the local news.
Today's high-end productions, documentaries, and news magazines demand a warmer look. You can trick your camera's white balance circuitry to achieve a warmer hue. A slightly warmer tone can improve your video considerably -- particularly with interviews.
A warmer white balance will give the subject a healthy, lightly tanned skin. The right white balance setting can give your video that "special something". When you balance to a standard white card or a WarmCard, you are telling the camera to make whatever color is on that card white.
To get a warmer look, you need to white balance to a different colored surface -- such as a WarmCard. Using WarmCards for color balancing is simple. You just hold one of the cards in front of the lens, hit the white balance switch -- and you're done. Once you learn to recognize different color temperatures and how to override a normal white balance, you can begin to turn ordinary shots into an extraordinary ones.
The common technique of white balancing by pointing the camera at a piece of scrap paper, snow, clothing, painted wall, or other supposedly "white" object is simply WRONG and lazy. Why? Unless the camera is white balanced in a consistent manner, shot-by-shot, then your footage will certainly appear wrong -- especially on skin tones! And it's people who are the main subjects on television over 90% of the time. If they don't look right, nothing will look right.
NOTE: White Tee-shirts are NOT white, they are light dingy gray, even if they're new and clean, so don't use someone's Tee-shirt to white balance. White skin is more critical than dark skin to variations in color temperature and care must always be taken to avoid any green or blue tones on white skin.
After you've tried WarmCards, you'll soon notice that people usually appear ill under a standard white balance. By comparing a standard white balance to a WarmCards white balance on someone sitting under interview lighting, you will soon appreciate the difference.
How to White Balance
Before white balancing, you need to check the camera's filter wheel to be sure you using the best filter for the current lighting conditions.
Fill the whole screen with the white reference. Anything less can result in an improper white balance. So, fill the frame, set the iris to auto, and expose the card so it registers close to peak.
You must select your white reference with care.
You should always carry a clean, rigid, white card or WarmCard. Ideally, you should use the same reference white throughout a shoot.
Care must be taken in positioning the card. Make sure it is held so that the primary source of light to which you want to balance is the only illumination falling on the card.
You may need to move from the shot position to do a white balance, in order to ensure that your main source of illumination ('white' light) is the only one falling on your white card. Make sure that the card is held steady, and that its angle avoids reflections.
Train your crew that they must not move the card at all until you're satisfied with the balance. If the card is accidentally moved while the camera is white balancing you may pick up reflections of unwanted light.
The card should always fill the frame. The camera must be properly lined up with the card, and if it isn't, the white balance values can vary from by several hundred degrees.
Activate the white balance by pressing the button. The camera may take a few seconds to complete the operation, after which you should get a message in the viewfinder telling you that the white balance has succeeded.
The camera will retain it's current balance until another white balance is performed. If the viewfinder message says that the white balance has failed, then you need to find out why. A good camera will give you a clue such as " temperature too high" (in which case change filters). Also check your iris and focus, and try opening or closing the iris a little.