The images were rendered using the Rendertoolbox software (http://rendertoolbox.org). The directories ImageSet1 and ImageSet2 contain the Rendertoolbox condition files and spectra required to render the images, once you have the toolbox installed and working. To produce the illuminant spectra, CIE Lab values for the illuminant were specified by hand, relative to D65 white point. These were then used to produce spectra within the specified illuminant linear model. To produce surface spectra, the mean and covariance of a truncated Gaussian was estimated from a dataset of Munsell surface reflectance spectra, and the covariance was doubled. Then individual ensembles of reflectance spectra were produced by perturbing the mean and covariance matrix, drawing weights, and reconstructing spectra within the surface linear model. Spectra with reflectance outside of the range [0,1] were eliminated. Different ensembles were used for different images. All of the surfaces in images 1-5 were matte. In images 6-10, different BRDFs were used for some surfaces, based on the isotropic Ward model. The Ward model parameters are given in the Rendertoolbox files. The Matlab programes GenerateSpectra in each of the two Rendertoolbox directories produce the illuminants and ensembles of surface reflectance. The Rendertoolbox image directories produce more images than we posted for the contest. The program PullOutContestImages pulls out the images used for the contest into a separate directory. This program is provided, and produced the folder ContestImageData.