> Is my assumption correct that the point of light from the missile's first > stage is four times brighter from half the distance? No. It is true for point sources and might be true if your shot is wide angle enough that the missile will look no larger when you get closer but I doubt it. For extended objects like this (think more than one pixel -- even if you use film it's easier to think of pixels), getting closer means more light into the camera but spread out over more film. e.g. if you are filming grass during the day and you get closer to the grass, you don't need to stop down the camera. Now if the blurriness of your lens is so bad or the object is so far that being twice as close looks like the same size on film (true with stars for example), then closer *is* brighter and twice as close would be four times brighter or 2 f-stops. - George Roberts ------------------------------------------------------------------------- Subscribe/Unsubscribe info, Frequently Asked Questions, SeeSat-L archive: http://www.satobs.org/seesat/seesatindex.html
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