All functions, features and firing modes were tested. To check the actual versus the claimed power, each flashgun was set to full-power manual flash, with a zoom setting of 105mm (FX). A flash light meter was used at a distance of two metres, and resulting readings were converted to give a guide number (Gn) at ISO100, measured in metres. We measured power output throughout the manual power range for each flashgun.
We tested each flashgun under the same conditions in order to make a fair comparison
Additional tests included checking for colour accuracy. A colour test chart was shot purely under flash illumination, using the camera’s Flash White Balance setting. For TTL flash exposure accuracy, we photographed a neutral grey card, which would produce a spike at the centre of the histogram display, and then we calculated the amount of overexposure or underexposure in +/-EV (Exposure Value) stops.