Software determination of gold particle locations. A, enlarged image of raw bitmap showing 6 gold particles. B, 3-Dimensional plot of A illustrates the difficulty in threshold detection of particles. C, the original bitmap convolved with a kernel comprised of the average of 662 gold particles; compare to B with respect to enhancement of gold particle signal and reduction in noise and intensity drift. D, software determination of gold particle locations, based on the center of mass of supra-threshold clusters of pixels. All spatial axes are in units of pixels, coincidentally similar in this instance to the dimensions in nanometers (see calibration in A).