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

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

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.

perhaps the most important problem we are facing.

I got quite good results from protein plates.