Adjust levels for "AboveLeft". Select output levels 127 and 0.
AboveLeft:
after levels adjusted
Step 5:
Create a new image (hereafter called "BelowRight"), with your Below-lighted photograph for a green channel, and your Right-lighted photograph for a red channel
BelowRight:
green channel = Lighted From Below
red channel = Lighted From Right
Step 6:
Adjust levels for "BelowRight". Select output levels 128 and 255.
BelowRight:
after levels adjusted
Step 7:
Paste BelowRight into a new layer over AboveLeft. Set the new layer's blend mode to "Overlay," and flatten your image.
(Optionally, experiment with other blend modes. I find "Hard Light" works well for some maps).
Normal Map:
after image overlay
Step 8:
Fill the blue channel with a light color. Experiment with the shade; a lighter blue will yield a smoother normal map.
Normal Map :
blue channel lightened
Step 9:
Apply NVIDIA's Normal Map filter, using the "Normalize Only" setting. Your normal map should now be finished and ready for use
