In the case of composite colour, an infinity of systems must be obtained for maxima infinitely slight and with an infinity of interval values separating them - that is to say, the whole thickness of the sensitive layer is occupied in continuous manner by these maxima.

In a paper delivered to the Philosophical Society of Glasgow on 17 January 1883 John G. Extremely fine-grained high-resolution photographic emulsions are inherently much less light-sensitive than ordinary emulsions so long exposure times were required. His father Isaïe a French Jew born in Ennery near Metz managed the family glove-making business at the former convent in Bonnevoie.