Archived posting to the Leica Users Group, 2006/01/10
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]> Another factor about tungsten light souces is that they more correctly > treated as point sources even when relatively close to them so light > intensity falls off inversely proportional to distance squared. > > But flourescent fixtures typically look like planar sources or line > sources which, if you're relatively close to them (and if I'm > remembering my rad-con rules of thumb appropriately) fall off just > inversely proportional to distance. (Assuming the ceiling is > reasonably low). In Western countries (or everywhere now I guess) where regular wall voltage is AC, incandescent sources cannot quench between cycles and therefore give the ilusion of a constant emmision. Fluorescents, however, do flicker at 50-60 Hz and can give a peculiar "banding" to negatives shot at shutter speeds faster than 1/60. I have learned to shoot at a 60th or lower in fluorescent lighting wherever possible to reduce the possibility of uneven lighting in the negative (it looks like the 2nd curtain stuck for a moment). JB > > This would account for tungsten sources giving you a hard time because > light fall-off across an image would be more severe. > > I've not looked at the spectrum of most incandescent bulbs but for > most vendors you can find those graphs on the net and compare them to > the published response graphs of the film you use. > > I'd never thought about light in quite these terms before. D'oh! > > Adam > > > _______________________________________________ > Leica Users Group. > See http://leica-users.org/mailman/listinfo/lug for more information >