Submitted version of the thesis - Airlab, the Artificial Intelligence ...

60 Chapter 5. Vision
may occur using auto white balance when the conditions listed above are
violated. Therefore, auto white balance may not be a good choice if:
• Absolute color accuracy is required
• There is a lot of one color in the scene: The preponderance of one
color can fool the auto white balance function into assuming that the
light has a lot of that color in it. This can result in an incorrect white
balance and a color cast.
• No adjustments made for the temperature of the light wanted: In
certain cases, the color of the light is what makes the photograph. A
sunset is an example. Without the rich, warm colors of the light, a
sunset just isn’t a sunset. Auto white balance may attempt to make
adjustments to correct for the warm color of the sunset light. This
would produce an image with less saturated colors or colors that were
different than what has been seen.
The camera we are using supports different settings for the balance. These
are:
• OFF - No White balance, all gains will be unity in this mode
• AUTOMATIC - Automatic mode, relative step is computed here
• MANUAL RGB - User manual mode, gains are applied manually
• DAYLIGHT PRESET - DAYLIGHT and all the modes below, fixed
value of gains are applied here.
• TUNGSTEN PRESET
• FLUORESCENT PRESET
• HORIZON PRESET
• MANUAL color TEMP
• FLASHGUN PRESET
Among the possible options, we set the white balance OFF. Because, in
the application we require absolute color accuracy and we don’t want the
camera to change the temperature of the color since we want to detect the
target with a constant color parameter defined using the samples we took.