As you know, Bob, noble metals such as silver and gold reject vampires. Thus, a vampire cannot be seen in a mirror, because the mirror is made with silver. It cannot be photographed, because silver is used in film emulsion. Presumably a vampire could be seen in a mirror made with a base metal such a mercury, or photographed with a digital camera which does not use silver-based films. (But could the image of the vampire pass through the camera's contacts? Contacts in electronic equipment are frequently gold-plated.)
What interests me is this: what effect would noble gases have on vampires? I've never seen this question addressed. Would a room full of argon, say, reject a vampire, the way a pool of water blessed by a priest rejects a witch?1 Might an atmosphere of 10% helium cause harm to a vampire? Besides ruining his dignity by making him talk like a duck, that is.
1. This is the reason you often see pools of blessed water used as trampolines by witches on holiday.