From The Art and Popular Culture Encyclopedia
Combination printing is the technique of using two or more photographic images in conjunction with one another to create a single image.
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 subject, such as a building, but would completely overexpose the sky. The sky would then lack detail, usually appearing as solid white. Hippolyte Bayard was the first to suggest combining two separate negatives, one of the subject matter and a properly exposed negative of clouds, to create a balanced photograph.
The technique was also used to create new, original compositions. Photographers such as William Lake Price and Oscar Rejlander are famous for using combination printing. Rejlander's Two Ways of Life is one of the most distinguished examples of the technique, combining 32 negatives to create the final image.
Controversy broke out in the photographic community about the use of combination printing in the mid-19th century. Photographs originally had been regarded as truth and that the camera never lied. However, with the ability to manipulate the final product, it shattered the notion that photographs depicted "truth."
The technique paved the way for yet another artistic process, photomontage.