Fig. 14. (A) Set-up to observe images of two solid squares side-by-side in a microscope. Solid squares of 1 mm and 10 mm are placed at distances of
10 mm and 100 mm from the isolated corneal lens, respectively. Both squares are black, but given colors as an aid to illustration. (B) The microscope
objective is focused on the nearby 1 mm-square in the upper micrograph, whereas it is on the distant 10 mm-square in the lower micrograph. The focused
image is marked by F. (C) Density distribution measured along white lines in (B).