sentences:  (Dufaycolor used similar principles, but had the filter as part of the film itself).Filming required the camera to be used at f/1.9 only, so that the striped filter worked correctly.The original Kodacolor film required an exposure of about a 1/30 second at f/1.9 in bright sunlight representing a film 'speed' (sensitivity) in modern terms of about 0.5 ISO.