Secrets of White Balance

What is White Balance?

Basically it is the light colour temperature. A low colour temperature shifts light toward the red; a high colour temperature shifts light toward the blue. Different light sources emit light at different colour temperatures, and thus the colour cast. With digital cameras, we can simply tell the image sensor to appy a colour shift.

This is where the concept of "White Balance" comes in. If we can tell the camera which object in the room is white and supposed to come out white in the picture, the camera can calculate the difference between the current colour temperature of that object and the correct colour temperature of a white object. And then shift all colours by that difference.

Although there are built-in white balance presets, you can manually set the white balance. It is very simple, point the camera at a white or gray card (angled so that it is reflecting light from the room) as a neutral reference, filling the screen completely with it, then pressing the White Balance button (or set it in the menu), the camera does its WB calculation. Now any picture taken will have its colour temperature shifted appropriately. When the lighting situation changes, you should adjust the custom white balance accordingly.

There is a number of add-on products available on the market that help you set the White Balance manually. They are based on two methods:

  • Reflective-Style White Balance method (meaning that you measure the white balance with a gray card or other remote object that light leflects from)

  • Incident TTL-Style White Balance method (meaning that you put a special cap on your lens and capture the white balance through the cap)
This article gives a list of products to choose from:

  • When using a gray card, ensure the card is not in shadows, but illuminated by the artificial light in the room. If you are bouncing light off the walls, ensure the card is reflecting the bounced light.

  • In mixing artificial lights situations, it is advisable to use RAW and adjust in post processing for each light.

  • Beware of fluorescent light: since fluorescent light does not contain all the spectrum of light, you may obtain unexpected results.

  • Pictures of snow scenes typically reproduce the snow not as white but with a bluish tinge. Sometimes, the blue adds to the mood of the picture, but at other times you may want to remove the blue.

  • If you are taking landscapes, and it's early in the morning or late in the evening, or you are not too sure of which WB setting to use, try it in RAW.

Preset White Balance

If setting your custom white balance is too much of a pain to you, cameras provide preset WB settings such as, Tungsten, Fluorescent, Cloudy, Sunny, etc. Such WB presets can improve on a picture, especially under indoors lighting.

Besides custom WB and WB presets, digital cameras are equipped with an Auto White Balance (AWB) function. Usually AWB works very well in sunny and cloudy outdoors, and fine for most indoors situations (a little orange or bluish cast does sometimes contribute to the mood of the picture anyway, e.g. the warm orangle glow of a candle). In most cases Auto WB does a pretty good job in diverse situations, outdoors and indoors.

RAW File Format

When you save an image in RAW file format, you are saving it the way the image sensor sees it -- without applying any adjustments (including white balance) to it. In fact, the camera ignores any WB setting you dial in. If you opt for shooting in RAW format rather than JPEG and you have an image editing software with the appropriate RAW plug-in, you can convert the RAW image to JPEG, and apply any colour temperature shift. This editing can be done again and again until you are happy with the color temperature in your photo.

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