One method of white balancing in Photoshop involves:
- Adding a difference layer filled with 50% grey over existing image.
- Adding a threshold layer over that and sliding the slider to the left until just a small handful of black dots are left.
- Using the eyedropper tool with shift to mark one of the clusters of black pixels.
- Hiding grey and threshold layers and creating a curves layer then using the grey point eyedropper to sample the point marked in the previous step.
This method works very well. Can someone please explain why this works? Are there cases where this doesn't produce the best results?