While random-surfing through various comp-sci sites looking for something vaguely photography or graphics focused that would also satisfy the programmer in me, I came across a series of articles from the 90s about synthetic lighting.   The premise is that you separate out each light source in a scene, including a shot of ONLY ambient light in order to allow you to do neat things with the lighting in post.   Reconstructing lighting in a physical scene within a digital scene, alterations of light levels, colors, intensities, etc…  even creating ‘negative’ lights that subtract light from a scene.    All of this is the bread-n-butter for 3D artists, mainly because their  entire world is synthetic.   However, for photographers it’s a bit more complicated.

After reading several papers and blog posts about it, I decided to try my hand at a simple demonstration of the technique.   What I did was take a static object and shoot three shots of it.   One ambient, one with a strobe on the left, and one with a strobe on the right.   Then, using some photoshop magic, created an interesting synthetic lighting setup that let me do somethign I could only have done with gels and a lot more fiddling with light levels.

Rather than talk about, let’s get down to the fun.  Get your camera out, take an ambient shot and a shot with each of two lights individually lighting the same object.  LOCK DOWN the camera, lights and object.  You’ll be compositing all three shots together a couple of times during all of this.  Everything has to line up perfectly.