Used in conditions where AWB (Auto White balance) is unable to detect and use a white image to auto set the white balance. Basically, you fill the frame with what you know to be a white object (even under colored lighting), this is saved as the camera's "white" reference and camera now auto-white-balances using the new reference "white" instead of it's internal reference.
ATW: Auto Tracking White Balance
ATW is a more dynamic version of AUTO white balance. It detects when your ambient lighting shifts significantly (such as moving from indoors to outdoors) and dynamically changes the AWB for you.
You Set the white balance options based off of Red and Blue gains.
Automatically detects light in the room and selects the best white balance option for you.
Preset settings for indoor camera use.
Preset settings for outdoor camera use.