Method, transmission unit, system and computer program for wireless communication between a camera and at least one remote flash device

A method for controlling flash power of at least one remote flash device and for synchronizing preflash occurrence with measurement using a camera at a point in time when light is captured, using an intermediate radio transmission unit for wireless transmission of radio signals to the remote flash device and for bi-directionally exchanging signals with the camera via a physical connection between the intermediate radio transmission unit and the camera, the method comprising the steps of:

• the camera transmitting to the intermediate radio transmission unit a preflash activation signal,
• the intermediate radio transmission unit starting a timer causing a delay, which delay together with a subsequent time period for forwarding the preflash activation signal to the remote flash device and another subsequent time period for the remote flash device to receive and transform the preflash activation signal into emission of light energy, the delay together with subsequent time periods being adapted to coincide in time with a predetermined delay between the point in time when the camera transmits the preflash activation signal and the point in time when the camera initiates capture of the light emitted as a preflash by the remote flash device coinciding with the predetermined delay,
• in dependence on preflash image analysis based on the captured light, determining a flash power change to be applied during a main flash subsequent to the preflash,
• transmitting, from the camera via the intermediate radio transmission unit to the remote flash device, the flash power change for the remote flash device to apply during the main flash, and
• transmitting, from the camera via the intermediate radio transmission unit to the remote flash device, a main flash activation signal upon which the main flash and image acquisition occurs.