reproduced photographically rather than added in by hand), as well as the earliest extant natural color photographs of San Francisco. Stereoscopic photography In 1903 Ives patented the parallax stereogram, the first "no glasses" autostereoscopic 3-D display technology. A compound image consisting of fine interlaced vertical slivers of a stereoscopic pair of images was seen in 3-D when viewed through a slightly separated fine grid of correctly spaced alternating opaque and transparent vertical lines, now known as a parallax barrier. The grid allowed each eye to see only the slivers of the image intended for it. Ives first exhibited such an image in 1901, at which time he stated that the basic concept had occurred to him about sixteen years earlier while working with line screens for the halftone process. In 1904, Auguste Berthier came forward to claim due credit for the first publication of this concept. He had included it near the end of an 1896 article about large-format stereoscopic images. Berthier had also created an extremely coarse and nonfunctional interlaced image for purposes of illustration, but he never reduced the idea to practice or attempted to patent it. Eventually, several other inventors, including Ives' son Herbert, substituted an array of narrow cylindrical lenses for the simple parallax barrier and incorporated more than two viewpoints, creating lenticular parallax panoramagram 3-D images of the type most familiar from 3-D postcards, trading cards and similar novelties, often confused with holograms. The original parallax barrier method is currently (2017) employed in several no-glasses 3-D video displays. Ives also patented the use of parallax barriers for displaying changeable images. As early as 1900, Ives was tinkering with stereoscopic motion pictures. By 1922, he and fellow inventor Jacob Leventhal were producing a popular series of anaglyph 3-D novelty shorts called Plastigrams. The first one was released by Educational Pictures in December 1922, and the later ones by Pathé Films. Halftone process Halftone processes allow photographs, complete with their "half-tone" intermediate shades of gray or color, to be reproduced in ink on paper by means of a printing press, like text. Prior to such processes, images were printed in books and periodicals by means of hand-engraved metal plates or wood blocks, or from drawings made on lithographic stones. Half-tone effects were obtained by engraving closely spaced parallel or hatched lines, by stippling, or by exploiting the granular texture inherent in the stone lithography process. Ives is