Since there's no reputation reward or stack-exchange virtual stickers for it, I'm using this space to say thanks to @scottbb for valiant effort to save the filters tag, by making it refer to actual, real-world filters rather than digital post-processing filters. This is a bit quixotic, but, hey — it does make the thing a bit more useful than having it as a mess of "effect" and physical filter questions mixed together.
People are still gonna keep coming by and using it for Instagram questions (or, you know, "What filter do I need to take pictures like I saw in National Geographic?" — *sigh*), though, so we will need to either keep a constant eye on it, or come up with some non-ambiguous synonym and use that instead. I don't have any ideas though, so... opening discussion. :)