Photographic images are found in museums, archives, and private collections in a bewildering variety of types and sizes. The care and storage of photographs differs from that for other works of art on paper because of their structure and materials. Most commonly they occur in the form of negatives or as positive prints on paper. The carriers for negatives are usually transparent glass plates or plastic film, but translucent paper was also used as a support material in the early days of photography, from the mid 1830s to the late 1860s. In the nineteenth and twentieth centuries, glass plates and plastic film also served as carriers for black-and-white positives known as lantern slides. Yet other nineteenth-century photographs, such as daguerreotypes or ambrotypes, can be either negative or positive, depending on how they are viewed. While the majority of older photographs made before the 1950s are black-and-white, most photographs taken during the last two decades are in color. Color prints today are commonly made on a resin-coated paper base (RC paper), but some have a plastic support made opaque through the inclusion of white pigments. Color negatives and color transparencies in various formats are found in increasingly greater numbers in collections.