Speedlight external battery with DIY battery plugs. I've made short movie how to create it:
No extra post processing (besides raw conversion to jpeg, cropping), taken straight from camera.
There are some notes on that photo.
- sb25 through white brolly,
- two 45Ws flash bulbs on background,
setup here (some additional words in Polish, but You will understand the most important things without knowing the language):
update: details of the plug