Measured output of flash Fresnel lights.

[Neal Chaves]

I have been interested in learning about and using flash Fresnel lights (Norman FS 6 and FS 10) for some time. I need light for large format photography, but I don't use films slower than 100 ISO. Some users of plate processes are lighting with large electronic flash(4800WS) from a beauty dish.

I know that a diffused and polarized Norman FS10 throws a very nice light many times brighter than a beauty dish, so I just made a rough measurement of output from the Norman at 2400WS, and from a Dynalite-converted Castor 10" Fresnel at 1000WS.

With the FS10 at 10 ft. from the meter. Light set to flood 2400WS equaled F45 at 100 ISO sync at 1/60 sec.
With the FS10 at 10 ft. from the meter. Light set to spot 2400WS equaled F64
With the FS10 at 5 ft. from the meter. Light set to spot 2400WS equaled F90

With the 10" Castor at 10 ft. from the meter. Light set to flood 1000WS equaled F22 at 100 ISO sync at 1/60 sec.
With the Castor set to spot at 5 ft. from the meter at 1000WS equaled F45

Looks like a flash Fresnel could be a practical as well as a classical way to light for those slow plates and films.