The rockstar crew behind Night Sight have created a neural network that takes a standard RGB image from a cellphone & produces a relit image, displaying the subject as though s/he were illuminated via a different environment map. Check out the results:

I spent years wanting & trying to get capabilities like this into Photoshop—and now it’s close to running in realtime on your telephone (!). Days of miracles and… well, you know.

Our method is trained on a small database of 18 individuals captured under different directional light sources in a controlled light stage setup consisting of a densely sampled sphere of lights. Our proposed technique produces quantitatively superior results on our dataset’s validation set compared to prior works, and produces convincing qualitative relighting results on a dataset of hundreds of real-world cellphone portraits. Because our technique can produce a 640 × 640 image in only 160 milliseconds, it may enable interactive user-facing photographic applications in the future.

[YouTube]