What Is White Balance?

Color image acquisition

A color image acquisition involves the use of three color filters on the camera sensor. Each color filter restricts the light source to a range of wavelengths of the light spectrum, either red (R), green (G), or blue (B).

An ideal capture system renders a white object as a white image. A white stimulation should yield the same signal for R, G and B filters. But practically, there are always unavoidable defects on the signals that introduce a white imbalance.

White imbalance factor

Several factors, due to the camera and to the capture conditions, are responsible for the white imbalance:

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Object illumination. The color of an object is a combination of its reflectivity and the spectral contents of the illuminating light.

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Camera optical filters response.

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Sensor sensitivity, which is not the same for the three ranges of wavelength.

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Different gain coefficients applied to each color signal before digitization.

White balance correction

MultiCam can correct the white imbalance of the capture system. The operation is called the white balance:

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The white balance operator applies correcting coefficients (R, G, and B gains) to each color signal, so, for a white object, the combination of the R, G, and B signals renders a white image.

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The white balance calibration is the computation of the three R, G, and B gains. It is performed on a representative image area, prior to the image capture. It can be automatic or manual.