Having been a serious amature photographer for more than 25 years and sometimes taking up to a 1000 frames or more a week (Many at night), these orb images were a genuine mystery to me and still are. This is the first time I have encountered them with this camera(or any of my SLR's -film and digital) in 1000's of shots.
I don't believe they are examples of digital artifacts that can be produced by many of today's pocket digital cameras, those are the result of increased depth of field because of the compact nature of these cameras and close proximity of the flash unit to the lens and dust particles floating in the air.
The digital camera I used is an SLR(Nikon D80 18-135mm) and was used with a lens hood and the flash disengaged- (sensitivity ISO -1200-1600) exposures about 1.0s -There was some ambient light from the sky and my car headlights (pointing away from the lens and the area where the orbs appeared)
I felt "compelled" to stop ahead of an intersection on top of a hill to take pictures for reasons other than aesthetic beauty. I had been surfing all afternoon and was pretty tired and thinking I couldn't be bothered setting up the camera, but luckily I did....
I keep my lenses in excellent condition and always check their clean before taking any Images. The focus range was set for about 25 meters away and with an aperture of between f5-f5.6 this results in a shallow depth of field at that focal point distance.
All of these factors seem to go Against the theory of it being a digital camera artifact, as these "false positive Orbs" need an extended depth of field within a few meters of the cameras lens to "appear".
Some conclusions from a site that explores the Science of Orb Photos(Mark Kimura, Ph.D) seems to support my pictures not being artifacts.
"In order for an orb photo to be classified as potentially paranormal, it needs to meet the following criteria:
1) A film SLR camera with a lens hood is used -(or Digital SLR with lens hood ?)
2) No flash is used- I did not use a flash.
3) There are no circular patterns inside the orb. (I need to post some close ups)
I believe that conclusion would lend weight to "my"orbs being of a paranormal nature, given the camera and method used to capture them. (without a flash it is hard to understand how these might " appear" in a darken portion of a photo)