A triggered air gap has been developed for inserting timing marks on the film of streaking cameras used in ultra‐high‐speed photography. The gap has a rise time ten times faster than existing xenon flashlamps. The peak output of 7 × 106cd/cm2(7Mcd/cm2) achieves the same film density as the lamps. This paper describes both the design used to achieve low inductance in the gap and the driving circuitry.