Fig. 1. Size affects shape. Except for size, the three objects are identical, yet, at reading distance, we see the large one as an ‘‘F’’, the medium one (1/8 as big) as an ‘‘E’’, and the tiny one (1/64 as big) as a ‘‘D’’. The letter you ‘‘see’’ and report tells us what frequency band your visual system uses to identify the object. Within the object, each component letter has been filtered to a one-octave band of spatial frequency. The first band is ‘‘C’’; the second is ‘‘D’’, and so on.  Majaj, N. J., Pelli, D. G., Kurshan, P., & Palomares, M. (2002) The role of spatial frequency channels in letter identification. Vision Research, 42 (9), 1165-1184. pdf