Nikon SDK https://sdk.nikonimaging.com/apply/ Camera Control Pro 2 English : http://imaging.nikon.com/lineup/software/control_pro2/ Japanese : http://www.nikon-image.com/products/software/camera_control_pro2/

"Direct HDR Capture of the Sun and Sky". Jessi Stumpfel Andrew Jones Andreas Wenger Chris Tchou Tim Hawkins Paul Debevec http://ict.usc.edu/pubs/Direct%20HDR%20Capture%20of%20the%20Sun%20and%20Sky.pdf