“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.”
Other Gabriel Lippmann Quotes
The problem of direct colour photography has been facing us since the turn of the last century.
Gabriel Lippmann 
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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.
Gabriel Lippmann
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The series of photographic operations, developing, washing, final drying, takes about quarter of an hour.
Gabriel Lippmann
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