under-exposed,ppl.a.Photogr. (stress var.) [under-1 10 a.] Of a sensitized plate or film: Having received too short an exposure to light. 1861in Wylde's Circ.Sci. (1865) I. 162 This is an..advantage when the picture is under-exposed.1878Abney Photogr. 81 An under-exposed picture will develop very slowly.