"When the shot is afterwards subjected to white light, colour appears because of selective reflection."

"Life is short and progress is slow."

"The length of exposure (one minute in sunlight) is still too long for the portrait. It was fifteen minutes when I first began my work. Progress may continue."

"I got quite good results from protein plates."

"The problem of direct colour photography has been facing us since the turn of the last century."

"The plate at each point only sends back to the eye the simple colour imprinted. The other colours are destroyed by interference. The eye thus perceives at each point the constituent colour of the image."

"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."

"This result is due to a phenomenon of interference which occurs within the sensitive layer."