Very quick­ly, black-and-white pho­tog­ra­phy ceased to be an end in itself. Dio­ram­ic views took a step towards colour by play­ing on the stereo­type, but some inven­tors used the stere­o­scope as a the­atre with illu­mi­nat­ing effects on glass views.
This was the case with Louis-Joseph-Auguste Gérard, who filed a patent (FR36.806 of 31 May 1858) for an improved stere­o­scope. Start­ing with a Brew­ster-type prism stere­o­scope that was entire­ly con­ven­tion­al for the peri­od, he added coloured glass rear diaphragms, mount­ed on hinges and adjustable in ori­en­ta­tion. Through their posi­tion­ing and the colour of the glass, these pro­vid­ed all the shades and nuances of day or night. The glass pan­els could be changed to colour rur­al scenes with light blue glass at the top and green at the bot­tom, adding a cer­tain charm to snowy moun­tain scenes with a del­i­cate vio­let tint above and green below. All shades were pos­si­ble depend­ing on the posi­tion­ing of the two or even three pan­els, and could be changed instant­ly accord­ing to the viewer’s mood. This stere­o­scope became known as the ‘Poly­chro­ma­tique’. Its adop­tion remained lim­it­ed, how­ev­er, per­haps because it was dif­fi­cult to oper­ate, since the appa­ra­tus had to be held while simul­ta­ne­ous­ly adjust­ing the pan­els and observ­ing the effects.
In July 1864, Jules Marinier also filed a patent (FR68.655) for a ‘Stéréo­scope mul­ti­col­ore’ pro­duc­ing the same effects with very sim­i­lar equip­ment. The only dif­fer­ences were, on the one hand, the inter­change­abil­i­ty of the coloured diaphragms at the rear by means of a remov­able hinge and, on the oth­er, the pos­si­bil­i­ty of replac­ing the reflect­ing pan­el with a coloured diaphragm for view­ing stereo­scop­ic cards.
(from: Moulin­ier et al. His­toires de vision­neuses stéréo­scopiques français­es. Limo­ges, 2025, p. 31. Author’s translation.)