A vampire would not show up on a digital camera
image, as the elements used to capture the pixels involve light receptive cells that are functionally the equivalent to mirrors. A vampire has no corporeal
form that any known physical device would be able to detect. (Outside of the bizarro end of quantum physics) They stand at the intersection between the plane of the living and that of the dead. They are neither in this world or the next, so any mechanism that can reflect or absorb light bounced off of matter in only one of these planes cannot detect them. Ergo, a digital camera cannot record a vampire.
A person can see a vampire as the human mind/spirit/whatever is bound to the plane of the dead by their inescapable mortality. We also have to bring in the fact that vampires can change their form, and influence the minds of mortals. The camera has no mind to influence (except maybe some fuzzy logic focussing mechanism, but that is probably too crude and artificial for the vampire's inate and ancient methods of hypnotism to affect).
Oh yeah, and vampires don't exist, negating the who argument.
But if the silver argument is true, why don't they have shadows? Except Nosferatu did. But it was cast by the Moon. Curiouser and curiouser.