Summary
Use the custom white balance when the ambient light is impossible to determine or there is a great mix of light sources.
In-Depth
The P-series has the ability to establish up to 3 custom white balance settings. These can be set with a simple point and shoot or click balance. The Custom WB is made available by pressing the WB button from the Main Menu. In the WB display, there are four additional options to choose from.
To make a new custom white balance, select Create WB and choose one of the three Custom #s. Once selected, the menu will display a blinking, Make Custom# WB . Make an image capture while placing the viewfinder center circle upon the area of choice. This can be a gray card or neutral white surface.
You now have a Custom white balance established, and it will be selected as the current capture white balance.
General about white balance:
Note that the Auto White balance should only be used when the ambient is impossible to determine. However - if the lightsource is known - please select the setting from the back or software menu. If the white balance is not satisfying then please use the Custom White balance function from the Digital back menu.