Stereoscope ‘Kromskop Color Stereoscope’ with Image Set

The Krom­skop was an ear­ly colour stere­o­scope devel­oped by Fred­er­ic Eugene Ives. It was part of Ives’s Pho­tochro­mo­scope sys­tem and was intend­ed to repro­duce pho­tographs in both nat­ur­al colour and stereo­scop­ic depth.
The sys­tem used spe­cial images called Kro­mo­grams. A Kro­mo­gram did not con­tain a sin­gle colour pho­to­graph. Instead, it con­sist­ed of three black-and-white stereo­scop­ic image pairs, each cap­tur­ing one colour com­po­nent: red, green, and blue-violet.
In use, the Kro­mo­gram was placed inside the Krom­skop. The instru­ment illu­mi­nat­ed each image through a cor­re­spond­ing coloured fil­ter. Trans­par­ent reflec­tors then com­bined the three fil­tered images opti­cal­ly, so that the view­er per­ceived one full-colour stereo­scop­ic image.
The qual­i­ty of the colour repro­duc­tion was wide­ly admired, but the sys­tem was mechan­i­cal­ly com­plex and expen­sive. It required spe­cial cam­eras, care­ful­ly pre­pared Kro­mo­grams, and a ded­i­cat­ed view­ing instru­ment. For this rea­son it remained a spe­cialised sys­tem rather than a mass-mar­ket pho­to­graph­ic process. Its com­mer­cial rel­e­vance declined after the intro­duc­tion of the Autochrome process in 1907, which made colour pho­tog­ra­phy sim­pler and required less spe­cialised view­ing equipment.
(from: Com­pendi­um of Stereoscopes)