[MF3D.FORUM:1472] Re: NSA MF slide show

[Tom Hubin <thubin@xxxxxxxxx>]

Bill Glickman wrote:
> 
> David
> 
>        A Guide Number 300 flash will do the following...
> 
> 300  Guide number of flash (in ft)
> 16    f stop lens setting
> 100   ISO
> 
>      With these variables, you can properly expose to these distances with
> these fl lenses....  If you need more light, then fire two flashes, just
> don't advance film if possible...or fire two flashes at once if you can, you
> will double the distances below for two firings...
> 
> 19 feet max. for 50mm fl
> 23 feet max. for 100mm fl

Hello Bill,

I am not familiar with these flash lamps but usually light intensity
falls off as the sqaure of the distance. So I would expect that 4
flashes would double the distance and that 2 flashes would only multiply
the distance by the square root of two or 1.4142 .

Tom Hubin
thubin@xxxxxxxxx