Effect of correction collar adjustments on the point spread functions of fluorescent microspheres. XZ cross section of 0.5 micron fluorescent microspheres mounted immediately below the coverslip with collar settings (A) 0.13, (B) 0.17, and (C) 0.21 mm. XZ cross section of 0.5 micron fluorescent microspheres mounted below 50 microns of fixed kidney tissue with collar settings (D) 0.13, (E) 0.17, and (F) 0.21 mm. Pseudocolor based on intensity. Scalebar = 2 microns, x=z.