Fig. 2.

Eye observing three stimuli, where θ is the same viewing angle for each; h. are the heights of each the object; d. are the distances at which each object size would result in the same retinal image. The d. to 1. is shorter than the d. to objects 2 and 3, but because the size of 1. is smaller than the others also, it results in the same viewing angle for each object at each distance