When taking pictures of subjects that are illuminated with fluorescent light using a digital camera it is possible that variations in white balance from image to image can occur. As a result, the overall color cast of the photograph can change depending on the exact instant that the shutter is released even thought the lighting conditions are constant. The reason for this phenomenon is that the color temperature of the light source changes during the power cycle. For normal AC lighting systems, the power goes from full to zero 100 times per second according to the variation in voltage. Incandescent lighting has a high thermal capacity (the filament remains hot) so the temperature and color remain relatively constant. Fluorescent lighting however uses a different method of illumination and the color will change from instant to instant. Our eyes do not detect this change as it happens too fast for us to recognize. However, the camera is able to capture an instant in time that the eye cannot, and when a picture is taken with a fast shutter speed these variations become noticeable. The phenomenon therefore occurs when the shutter speed is comparatively faster than the frequency of the AC power source to the light.
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