[MF3D.FORUM:1501] Re: GN for Multiple Flashes (Was: NSA MF slide show)

["Bill Glickman" <bglick@xxxxxxxx>]

Mike

       That was the missing formula I was looking for!  Thank you...

> Here's the math when multiple units are each at the same distance from the
> subject or when a single unit is fired multiple times from the same
> distance (multiple exposure):
>
>    GNtotal=sqrt((GN1*GN1)+(GN2*GN2)+(GNn*GNn))
>
> GNn is for the nth flash unit's guide number, so you can add as many
> flashes as you want to this formula.
>
> So, two identical flash units (or two firings of one flash unit) will give
> you one more stop, four units will give you 2 more stops, it takes 8 units
> to get 3 more stops, etc.
>
> Mike
>