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Most digital cameras have something called AWB (Auto White Balance). The theory behind AWB is that the average colour in all images is grey (refered to as 18% grey in photo texts). This works fairly well under most conditions, except when you're taking pictures under photographically challenging conditions (like an indoor rink under artificial lighting). The image on the left shows the results from using AWB.
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The second image shows the results from setting a CWB (Custom White Balance) with the camera setup to interpret the average colour of the first image as white. Although the camera has correctly compensated for the colour cast caused by the unusual lighting conditions it still assumes this is an average image and that it should (on average) be grey.
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To "fool" the camera into recording the image correctly you need to increase the exposure (thus overexposing the image). The third image is the result of overexposing the scene by 1 stop. The only drawback to this method is your shutter speed will decrease which may result in a blurred image.
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Notes:
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1. These images were captured as JPG's with a Canon 20d.
2. These in-camera adjustments aren't required if you're shooting RAW, although getting the proper exposure in the first place will save you processing time when you get back to your computer.
3. Colour compensation is so much easier in the digital age, with a film camera you would need to know the colour "temperature" of the lights and place a corrective filter in front of the lens.
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