Some of the more advanced copy cameras have a backlit copyboard, eg diffusion illumination, for copying slides and other transparencies. This makes it possible to make prints of large negs using the copy camera without any modification, just set it up for transparency copies. Some have a flourescent unit under the regular copyboard and you just need to take off the covering and turn on the lighting, others may have to have the lights swung around to the back of the copyboard to work.