Senna3's Fotothing

Painting of 19th century S. Tropez photographed with 30 sec. exposure time
Netherlands, Bussum, Nov. 2012

The Long Exposure Friday entry of Hallo intrigued me. In his contribution, originally white figures painted red light unequally at long exposure time (30 sec.): http://www.fotothing.com/hallo/photo/b6306ebd75c1b26a3af862642099ff2f/
I have never experimented with long exposure times and I didn't understand why colours would change so drastically. The above picture was taken in a completely dark room except for a computer screen with a rather dark desktop image at 3 m. distance of the painting. I reduced the brightness of the screen until the resulting photo was not anymore a completely white field. The colours are only a bit more blue than the original (see picture at the left).