File:RGB Dye Sublimation Panels.jpg
The black bars alongside each panel of color are timing marks used by the printer to locate the start of each panel. The one centered in front of the yellow panel is offset to indicate this as the first panel in the print, and is used to keep the printing synchronized in case the roll is pulled out and reinserted with the rolls manually advanced past the timing mark.
Photographed by Dale Mahalko, from a nearly obsolete 310dpi Sony UP-D2500 photo printer.