Prism Stereoscope ‘Le Benescope. Auto-Redresseur’

Georges-Adolphe-Emmanuel-Pierre Balmit­gère was born on Sep­tem­ber 3, 1871, in Algiers, and died on Novem­ber 4, 1918, at the age of 47. Very lit­tle is known about him, except that he became inter­est­ed in stere­oscopy and filed three patents and two addi­tions between 1907 and 1909, with a final one in 1918, six months before his death.
The prob­lem that would lead Balmit­gère to file his patents about stereo­scop­ic pho­tog­ra­phy, which already had its stan­dards, defined for­mats, and a stan­dard process to realise pos­i­tive slides, is con­nect­ed to the Autochrome plates by Lumière, which appeared on the mar­ket the same year, 1907. These, because of their com­po­si­tion of a three-coloured fil­ter and a black-and-white neg­a­tive, could only be direct­ly devel­oped into a pos­i­tive, keep­ing either their invert­ed posi­tion or requir­ing them to be cut for a rearrange­ment of the images to allow clas­si­cal stereo­scop­ic view­ing. Balmitgère’s solu­tion is an opti­cal inver­sion cov­ered by patent FR400318 of Jan­u­ary 27, 1909.
The stere­o­scopes designed by Georges Balmit­gère were con­struct­ed by Mat­tey and appear in the cat­a­logs of this man­u­fac­tur­er from the peri­od, but only around 1920.
The Benescope ‘Auto-Redresseur’ is a very sim­ple wood­en con­struc­tion with no par­tic­u­lar­ly dis­tinc­tive design. Its only notable fea­ture is the inte­roc­u­lar adjust­ment sys­tem. Notably, the left ocu­lar uses a mir­ror, while the right uses a prism with a spe­cif­ic opti­cal for­mu­la to com­pen­sate for the view­ing dis­tance and pro­vide both images with exact­ly the same magnification.
Avail­able in for­mats 45x107, 6x13, and 8x16. The mod­el name remains a mystery.
(from: Moulin­ier et al. His­toires de vision­neuses stéréo­scopiques français­es. Limo­ges, 2025, p. 192. Author’s translation.)