It’s just reflected sunlight.
Since when do vampires see reflections? 
Ha ha ha. You might have a point.
It’s not that vampires can’t see reflections, it’s that they don’t cast reflections in mirrors (presumably in things like water either.) That’s actually something I’ve always wondered about: can you videotape vampires, given that videocameras (back in the day) needed mirrors as focusing elements?
I’ve often wondered if you can photograph or film vampires (given that the image is produced by chemical means and not simple electromagnetic phenomena) even if you can’t videotape them.
As to the OP: I dunno. Maybe there’s a threshold of how much reflected sunlight can hurt a vampire. Maybe vampires are uncomfortable during a full moon, but a quarter phase, they’re okay with.
Why aren’t vampires affected by starlight? Sunlight is starlight.
Bram Stoker’s Dracula wasn’t much affected by sunlight; it just made him a bit tired.
I suspect this is something you need to interpret mythologically. Vampires are creatures of the night. Even though the moon is visible in daytime nearly half the time, mythologically, it’s an entity “of the night” and so harmless to vampires (and the same goes even more so for stars)
Well, you could get some clues if you look at a real-life analog, a disease called porphyria – more specifically a variant called porphyria cutanea tarda (PCT). It’s sometimes called “vampire disease” because it’s characterized by extreme sensitivity to sunlight. But symptoms are only triggered by direct exposure to sunlight, not moonlight, starlight, or most forms of artificial light. Presumably our favourite Transylvanian Count would be the same way.
I guess the Gold Coast Lost Boys are really into Jheri Curl? I much prefer the Central Coast vampires:
Stranger
A 25th Anniversary comic of Buffy the Vampire Slayer came out recently. It is a collection of short stories, and one involves Spike in the Disco era. He is standing in front of a mirror, and comments about how for all the terrible ideas people have had, using aluminum to back a mirror instead of silver was one of the great ones. I thought that was really clever, saying that it was the silver that was the problem. A twist I’ve never seen before.
Vampires are affected by moonlight. It doesn’t kill them. Maybe the intensity is too low? It makes them feel romantic. Nostalgic. Possibly a little peckish. What did you mean by “affected”?
Vampires have a hereditary disease that is called idiopathic plotitis. It is uncurable but also unpredictable. It may pop out at any moment or go thankfully unnoticed.
I think a scientific study of vampires and sunlight would determine that it is an intensity issue. After all, the sunlight that we get directly on Earth carries much greater energy than the reflected light that we get from the moon. It’s much brighter, for one thing, and also carries heat, that we don’t get from moonlight.
My hypothesis is that it is not sunlight per se, but the amount of sunlight-energy that is received by the vampire.
Clearly, a properly funded research program is needed to determine this issue.
I’ve heard this before as a reason for not casting reflections and as a reason why vampires can’t be photographed because silver is used in making and/or processing film
So…why don’t we have more pics of them now that nobody has a film camera anymore?
(Back when I worked in a film developing lab, we poured the into a barrel so the silver could be reclaimed. We amused ourselves by discussing how we could pour a barrel of used fixer at an attacking werewolf hoard. Yeah, we were bored.)
Who says we don’t?
I don’t know about digital photos but in the Buffyverse they could be seen on video
I get it. Some days I don’t like the moon or the sun glowing on me.
You can’t have a good hair or good skin day, every day.
Just how it is.
Right. They’ve got to be under the moonlight, the serious moonlight.
Vampires are magical, supernatural creatures. Nothing about them can be understood through scientific, natural examination.