Abstract: an external light source is designed as an external flashgun for mobile devices consisting of a xenon flash tube with associated electronic circuitry, whereby the external light source is arranged to operate in at least two modes, in the single flash mode and in the apparent uniform flash mode. The mode of the external light source's operation is set automatically based on the exposure time set on the linked mobile device. One or several external light source are arranged to connect to a mobile device via a radio link, whereby the external light source sends timestamps to the linked mobile device in regular intervals via the radio link. Based on the timestamps, an algorithm in the software running on the mobile device calculates the time delay between the moment photo capture starts on the mobile device and the moment of the flash of light being triggered by the external light source, resulting in the entire frame/subject/scene being uniformly lighted.