A glass container inspection machine is disclosed for inspecting glass stippled bottles for defects. Stippled bottles are supported at an inspection station and are illuminated with a light source. The stippled bottle is imaged a pixel matrix with the pixels of the image varying in intensity from bright to gray at the points of stippling. A computer evaluates the pixels of the image including a look up table for values to be assigned to specific light intensities from light to black, the plot of the look up table having a high gain portion from black to gray and a continuous low gain portion from gray to white.