Hi,
I have Olympus E-400 DSLR, I wonder why I get Green and blue spots on the photo whenever I shoot with Bulb mode for more than 15sec clearly seen on the dark part of the photo.
dead pixels. This happens on all cameras it's just a matter of time. With my D200 it happens when my exposures go over about 2-5min at ISO100 or about 1.5seconds at ISO800. Lots of cameras have inbuilt long exposure noise removal which work because it's usually always the same pixels which die at a given shutterspeed / iso.
Thanx for your replies, I here include a link to the photo taken at f/14 40sec the spots can be seen at 100% preview. Can you try with your cameras and see if you get the same results.