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 Combination printing Combination printing is the photographic technique of using the negatives of two or more images in conjunction with one another to create a single image. Similar to dual-negative landscape photography, combination printing was technically much more complex. The concept of combination printing stemmed from the desire to create more of a fine art within photography and often more idealized images. Combination printing was popular in the mid-19th century due to the limitations of the negative's light sensitivity and camera technology. For example, the long exposures required at the time to create an image would properly expose the main