In this stereographic photograph of a group of 3,000 U.S. soldiers (prepared to fight in Europe in WWI, ca. 1917/1918), there is a smaller contingent in two rows, in front, consierably removed from the rest of the formation. This is difficult to see in the first image. However, with a more concentrated view and deeper scan, this is a little more evident, below:
This view still shows the first row of soldiers; that more-distant third row differentiation is much more defined here--the depth of the mass of the formation is starting to really come into focus. The next image shows the heads of the men in the second row, but mostly concentrates on that third row, and beyond:
The final view is just above the heads of the sldiers in the third rank, and more clearly shows the those men in the rear of the formation, including that final rank, which is a profile of men marching. This enlargement represents a section in the original photograph that measures less than 10x6mm--60 square millimeters of great density, complexity, insight, and beauty.