The apparent contrast of a centrally viewed Gabor target patch was measured by contrast matching in the presence of Gabor flanking patches positioned on a ring of radius r from the center of the target patch. Central patch apparent contrast was determined as a function of the number of flanking patches, the radius r of the ring, and the contrasts of both central and flanking patches. The apparent contrast of the central patch was reduced by the presence of the flanking patches for all experimental conditions. A two layer non-linear model for contrast perception accounts quite well for the data. The first layer performs a power function transformation on the contrast signals from the patches. The second layer takes the outputs from the first layer and divides them by one plus the square root of spatially weighted responses of nearby first layer mechanisms.