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 one wavelength 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 factors
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 sum 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.