Rear projection was conceived long before its actual usage; however, it was only made possible in the 1930s due to three necessary technical developments. The most important was the development of camera and projector motors which could be linked up for synchronization of their shutters, which were developed out of the unrelated needs of "talking" movies whose timing had to be carefully controlled. Secondly, Eastman Kodak's introduction of panchromatic film stock in 1928 allowed for the camera to expose the projected background more than orthochromatic stocks, making it look less faint than it did before. Finally, the larger film gauges beginning to emerge in the late 1920s demanded more powerful projection lamps, which were subsequently available for making the rear projection screen brighter and thus more properly exposed.