Andy, If the two lights are closely spaced, and have identical spectra, the intensity of the light reflected from any surface that enters the camera will be reduced by 1/2 if one of the lights is removed. That's one stop more, or three in this case. Conversely, if two lights are two stops under, four lights will only double the intensity so we're now one stop under. We have to double the number of lights again to double the intensity, so eight lights in all. Is that the correct way to look at it? Roger On 19 Nov 2009, at 1:14 PM, ADavidhazy wrote: > David, > > on target ... I was in error about going to 1 - if 2 is 2 stops under then 1 is 3 as you say! > I have to pay more attention to detail!! > > andy > > > David Dyer-Bennet wrote: > >> On Thu, November 19, 2009 10:32, Trevor Cunningham wrote: >>> Not knowing a thing about the physics involved, I'm forced to ask >>> questions: >>> Does the proximity of the lights to each other make a difference? >> Not generally and theoretically. >>> How many stops of underexposure does one lamp produce? >> Three, in this case. > R
