We test all features for each flashgun. These typically include flash exposure compensation and manual power settings, motorized zoom heads and advanced flash modes like high-speed sync, rear curtain and, in some cases, strobe flash. To test power output, we used a Sekonic flash meter placed one metre from each flashgun. We check the complete range of manual power settings, in one-stop increments. Based on a sensitivity of ISO100, the figures correlate directly with the Gn (Guide number).
The results are double-checked by taking shots with the appropriate lens apertures and using the camera’s histogram display in playback mode. This is done for flash zoom settings of 24mm, 50mm and 105mm (in full-frame terms), where these are available.