Although I’ve been an active photographer for many years, mainly landscape and wildlife, I’ve never really got around to the use of Flash. The last few miserable months of rain has led me to start considering more indoor photography (portraits etc.) where flash would be essential. I’ve watched countless YouTube videos of studio Flash and lighting and done some experimenting with an on camera flash on my Canon 7D MkII. I’m now considering the next step and investing in an off camera studio flash. However, before I do I have a question which I hope members to this forum could answer, as I’ve looked everywhere and cannot find a sensible answer. Many of the videos I’ve watched the photographer states “I’ve got the flash on half power” or “the flash is on one eighth power” etc. but nobody seems to explain why they have made this decision. Is there some magic formulae which dictates whether you use full power, half power or even 128th power, or is it just down to trial and error and something that comes with experience?