Dilution experiment with fluorescently labeled samples. (a) A patch from the first dilution experiment with Cy3-labeled oligonucleotides on glass, showing eight replicates of a serial dilution. (b) Log2 background-corrected intensity values for the spots in the patch, going from left to right (dilution stages) and from top to bottom (replicates). The linear decrease shows that intensity is dropping as a power of concentration, but the slope suggests that this power is not what is expected. Note the consistency across replicates. sVol is the background-corrected volume, where volume is the density of each spot multiplied by its area, and density represents the average of all the pixels in the spot.