At Cornell we developed a new method for measuring the bidirectional reflectance distribution function (BRDF) using photographs of a curved surface. The idea is that a picture of a smoothly curved, convex surface illuminated by a point light source gives you a large collection of separate measurements of the BRDF. By using a sequence of photos we can measure the BRDF completely.
For more details, start by reading Chapter 5 of my thesis. It describes the first version of this system, which I put together with the help of Steve Westin and Eric Lafortune. Our Applied Optics paper also describes that version.
A newer set of measurements, which included the first known (to me) BRDF measurements of human skin, was done later by Steve Westin and Eric Lafortune, with my help. This version is described in our Eurographics Rendering Workshop paper, which was actually the first publication about the project.
Much of the data that has been collected using this technique is available from the Light Measurement Lab pages at Cornell.