Hi

I use a studio floor pack (around 4000 WS) with a couple of strip lights to shoot digital pinhole on a 5D with a home made bodycap. Shooting at 1600ISO on full power I get correct exposure at about 1.5 meters...

I did once check the flash output - I think it was somewhere around F96 on 100 ISO at around 10 ft..

I've also shot film in my zero 2000 - using ISO 800 I set my old Bowens 800 around 2 feet from the subject (using a reflector) and gave around 4 or 5 pops...

The trick is to get the flash as close as possible, and remember that for every stop extra exposure you need to double the number of flashes - if you give 8 flashes and want a stop more then give 16 flashes - 2 stops more give 32 flashes....

Cheers