How to adjust white point in Photoshop:
The Auto option for Levels and Curves and the Auto Tone command automatically adjust the black point and white point in an image. This clips a portion of the shadows and highlights in each channel and maps the lightest and darkest pixels in each color channel to pure white (level 255) and pure black (level 0). The intermediate pixel values are redistributed proportionately. As a result, using the Auto option or Auto Tone increases the contrast in an image because the pixel values are expanded. Because the Auto option and Auto Tone adjust each color channel individually, it may remove color or introduce color casts.
The Auto option and Auto Tone give good results in certain images with an average distribution of pixel values that need a simple increase in contrast.
By default, the Auto option and the Auto Tone command clip the white and black pixels by 0.1%—that is, it ignores the first 0.1% of either extreme when identifying the lightest and darkest pixels in the image.
How White Point in Photos Works:
While you can auto adjust the white point, in many cameras you can slide the temperature slider and when you like the results you take the picture.