The relativistic homo mensura of Protagoras1 seems to have two general meanings for current discussions of measurement: first, for the collection of data and, second, for its presentation-in other words, relativities regarding what shows up when we measure, and regarding how we show (display) our measurements to ourselves. Photography, as an important instrument of modern scientific measurement, provides clear and interesting illustrations of this, especially when we consider it historically, also according to its most common functions.