Orbs appearing in photographs might not be a phenomenon exclusive to digital or even modern photography, however, as this photo shows.
I recently bought a book of antique family photos from a local antique shop. While closely examining this photo of an attractive, unidentified woman, taken circa 1890, I noticed what seems to be a classic orb floating near her arm. The photo was probably not taken with a powder flash, as there don't seem to be any resulting shadows. Film and lenses in those days were very slow, and photos such as this -- especially taken indoors (this is a studio portrait) -- required long exposures. The subject had to stand quite still while the photographer uncapped the lens and exposed the film, possibly for several seconds. So if the orb is actually there, it would have had to be stationary as well.
Another possibility is that it is simply a developing flaw or tiny spot on the lens.
I welcome comments from professional photographers or photo historians.