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:
- Object illumination. The color of an object is a combination of its reflectivity and the spectral contents of the illuminating light.
- Camera optical filters response.
- Sensor sensitivity, which is not the same for the three ranges of wavelength.
- 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:
- 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.
- 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.