Evidence of the effect of ozone. (Top left) Depicting the spot morphology typically observed, first in ozone-affected arrays and then in undamaged arrays. Note the greater homogeneity of spot arising from the undamaged arrays when contrasted with the 'phases of the moon' demonstrated by the damaged arrays. (Bottom left) Depicting the log-intensities observed in the red foreground channels of first ozone-affected arrays and then undamaged arrays. Note that the damaged arrays show much greater inter-array variation, generally lower intensities and often much lower intra-array variance. (Right) A representation of the red channel from a particular ozone-affected array. Missing values (as are part of the design of the platform) have been replaced by an average of their neighbours' values to avoid distraction. Note the lower intensities in the upper, lower and right-hand sides, and the still-observable zig-zag of control spots approximately a quarter of the way in from the left-hand side.