How to Master your Digital Camera’s White Balance
Not all light is the same colour, but if you want to ensure great colour reproduction in your digital photographs, it’s necessary to appreciate the basic physics behind this phenomenon. A good place to start is with visible light. This is a stream of electromagnetic energy that is emitted when a material is heated. Most photographic light sources produce a mixture of all the visible wavelengths (that is, colours) of the electromagnetic spectrum, but the proportions of these wavelengths vary wildly from one light source to another.
The Kelvin Colour Temperature scale is a numerical representation of this colour balance, and is expressed in degrees Kelvin. It is based on the sequence of coloured light emitted by a material (such as iron) as it is slowly heated from room temperature to melting point. The sequence passes through red, orange, yellow, white and blue.
The lower the colour temperature, the greater the shift towards red light; the higher the colour temperature, the greater the shift towards blue light. In the Kelvin scale, candlelight is rated at around 1,900K and tungsten light between 2,800K and 3,400K. Meanwhile, noon on a sunny day is measured as 5,500K; electronic flash between 5,000K and 6,000K; and blue sky between 11,000K and 18,000K. Incredibly, our brains constantly adapt our vision so that white objects always appear white, regardless of the colour temperature of the light source. Cameras are far less sophisticated, and record the many colour casts generated by different light sources as they really are. Photos taken under household bulbs (which emit more red and yellow light waves than blue) will display a warm orange cast; photos shot under fluorescent lighting will exhibit a harsh green tint; and pictures taken either outdoors in the sun, shade, rain or with an electronic flash will err towards blue.
Digital Camera technology
Digital cameras dodge this problem via so-called white balance technology, by which they vary the balance of recorded colours to compensate for the colour temperature of the dominant light source. This is achieved by adjusting the output intensity of the light sensor’s red, blue and green channels in relation to a standard white colour. Most consumer digital cameras feature an automatic white balance setting, plus a number of preset modes related to specific lighting conditions, including daylight, shade, tungsten, fluorescent, cloudy, and flash. Advanced digital camera models also feature a custom white balance mode that lets you match the white balance to the lighting conditions manually. A number of professional SLRs let you dial in actual Kelvin values, but this option is best used in conjunction with a colour temperature meter.
Even the most advanced automated white balance modes can be fooled if there is a predominance of certain colours or a mixture of different light sources in a scene. For example, if you are shooting a sumptuous orange and red sunset, most cameras will cool down the scene to balance out the colours. The upshot? You can usually obtain more accurate results by selecting the preset white balance mode that most closely matches the lighting conditions.
However, because the presets group several light sources with different temperatures under the same umbrella, the results will still only be approximate. For example, fluorescent lights range from low-temperature stadium floodlights (2,700K) through to high-temperature mercury vapour lamps (7,200K). The colour of daylight also changes according to the time of day, time of year, altitude and weather conditions. If your digital camera offers white balance compensation, you can obtain more precise results by dialing in more warmth or coolness. White balance bracketing, in which the camera creates multiple copies of a scene with incremental colour temperature changes, is another excellent way to improve accuracy.
Manual White Balance
More accurate still is the manual setting, which involves photographing a white object, such as a sheet of paper under the light source in guestion. There will be occasions when time constraints force you to rely on automatic white balance. You can alleviate certain colour cast problems in a decent image editor, but it’s tricky and there are limitations. A more erudite solution to this problem is to shoot in RAW mode so that no white balance processing is done in-camera. Instead, chosen settings are saved as info tags that don’t affect the original data. Most RAW enabled digital cameras ship with software that enables you to make white balance selections and corrections in a non-destructive way. This method reduces the risk of noise caused by in-camera white balance conversions. The only major downside is the increase in postprocessing reguired so, wherever possible, try to get the white balance right at the time of shooting.
Tagged with: colour • Flash • Light Source • lighting • RAW mode • temperature • White Balance
Filed under: Photography Tips
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I am wondering what are the main difference setting up the white balance vs the macros functions?
And some digital cameras included with different scene modes as well, will it helps to maintain the white balance that we expected?
Many thanks…