When I teach my film making course it’s always necessary to explain what white balancing your camera is all about and why you must do it. Many of my students are beginners whose only video camera experience is with a consumer camcorder that does not allow for manual white balance. Over the years I’ve honed my explanation down to the essentials.
Consumer cameras and many professional models as well will have an automatic white balance feature which is very handy when you are quickly moving between different lighting situations and haven’t the time to manually white balance (eg. when moving from outdoor sunlight to indoors tungsten or fluorescent lighting during a documentary shoot). While auto white balance is great under perfect conditions it’s never bang-on accurate and under difficult lighting conditions can often give you a weirdly colored picture.
The color of light is measured in degrees Kevin. Outdoor, bright sunlight weighs in at about 5600° Kevin while indoor tungsten light (standard light bulbs) is around 2700° K.
Fluorescent light is somewhere between 3600° to 4000°.
In practical terms this means that outdoor light has a blueish tinge (caused by the way light is scattered through our atmosphere), tungsten light is somewhat orange or red and fluorescent light is kinda green.
If you do not properly color balance your camera before shooting you might end up with tinted pictures which do not mimic the colors as seen with the naked eye in that setting.
Color balancing is usually quite easy. Simply fill your frame with a white image such as a proper white card or a white piece of paper - which is positioned to reflect the lighting in your setting - and press the camera’s white balance button until the display says it’s done. However, the eye can be tricked into thinking that something is white when it’s really a few shades off from pure white. So, avoid using the side of a “white” car, a “white” wall or the front of a “white” refrigerator. These things are rarely pure white. Best to invest a couple of dollars in a proper white card from your local photography store.
The camera uses the color white (which is really an even mixture of the red, green and blue spectrums) to determine the proper tonal shift for all colors from one lighting situation to another.
Many of my students either forget to white balance at all - or - white balance every time the camera is moved from one position to another. This is not always necessary. You need only re-balance the camera when the lighting is different. If you just move around within the set and the lighting has not changed you do not need to re-balance.
Although, if your shoot is outside and spans early morning through to the afternoon or afternoon to early evening you might be wise to re-balance every hour or so. The reason for this is that when the sun is high in the sky we’ll have our blueish 5600° Kelvin. But when it’s nearer to the horizon it will be redder. You’ve probably observed that sunrises and sunsets cast a red hue on the clouds.
All in all, color balance whenever you think the light has changed significantly.
Tweaking the overall color a bit in post production is possible, but certainly not the preferred method of matching the color of your shots.
Color balancing is explained in more detail in my book at:
http://www.mikesdvp.com
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