Gum bichromate negatives of cyan, magenta, and yellow or red, green, and blue are used for a full-color image. Some photographers prefer substituting the cyan emulsion in the CMYK separations with a cyanotype layer. A simple duotone separation combining orange watercolor pigment and a cyanotype can yield surprisingly beautiful results. Low density photographic negatives of the same size as the final image are used for exposing the print. No enlarger is used, but instead, a contact printing frame or vacuum exposure frame is used with an ultraviolet light source such as a mercury vapor lamp, a common fluorescent black light, or the
Combination printing often necessary to add artistic techniques to photographs. Discussing the benefits of composition in the art of photography and using combination printing, Robinson wrote, in "Pictorial Effect in Photography", that the method of combination served to "produce an agreeable presentation of forms and tones, to tell the story which is to be elucidated, and to embody the spirit of what it is intended the picture shall represent or suggest." His writings show his knowledge and his passion for creating new content in his photos with using this process. During the Victorian Era, another proponent of the technique of combination printing