The production of photographic three-color prints on paper was pioneered by Louis Ducos du Hauron, whose comprehensive 1868 French patent also included the basic concepts of most of the color photographic processes which were subsequently developed. For making the three color-filtered negatives required, he was able to develop materials and methods which were not as completely blind to red and green light as those used by Thomas Sutton in 1861, but they were still very insensitive to those colors. Exposure times were impractically long, the red or orange-filtered negative requiring hours of exposure in the camera. His earliest surviving color prints are "sun prints" of pressed flowers and leaves, each of the three negatives having been made without a camera by exposing the light-sensitive surface to direct sunlight passing first through a color filter and then through the vegetation. His first attempts were based on the red-yellow-blue colors then used for pigments, with no color reversal. Later he used the primary colors of light with color reversal.