Biological specimens are recognized with a matched spatial filter (MSF) made from their simulated pattern. The partial correlations between the simulated pattern and the various sized specimens show that the simplified filter is considerably less sensitive to the size variation while it still retains a high degree of pattern discrimination against other species.
Silverio P. Almeida,
"Partially Matched Spatial Filtering With Simulated Input", Proc. SPIE 0177, Optical Information Storage, (10 July 1979); doi: 10.1117/12.957240; https://doi.org/10.1117/12.957240