"Lens flare" clarification

What exactly is the lens_flare tag meant to be used for? The current wiki is too vague and focused on the optical mechanisms that produce it in photography, rather than what it actually looks like.

I've always understood lens flare to refer to the artifacts shaped like circles, hexagons, octagons etc. like in post #1602064. But it's also apparently used for images where a light source, or a reflection of one, is stretched out in one or more axes, like in post #1600945. The two can occur together (the first example has stretching in the reflections on the jewelry) but you can also get one without the other.

I think these ought to be distinguished but I don't know what to call them. We also need to distinguish between the first kind of lens flare and bokeh, though that might be hard sometimes.

As far as I know, the horizontal "stretching" kind of lens flare (e.g. post #1600635) is produced by some kinds of lenses (IIRC the 2009 Star Trek film had these everywhere) as the actual blooming around the bright light source, accompanying the usual "string-of-circles" artifacts. No idea about in different directions as you posted - I suspect it's just an artistic effect rather than a reproduction of anything that happens with real cameras, but I'm no photographer, so I can't say for sure.

It's easier to tell apart lens flare and bokeh just by eye than it is to explain how (at least I'm certainly finding it difficult here...), but bokeh is produced by light sources in the frame but outside the camera's depth of field (i.e. out of focus). I suppose one way to look at it is that the circles from lens flare are completely original artifacts over top of the image (without lens flare, there wouldn't be any purple circles floating there) while bokeh is just the same image, but out of focus (without bokeh, i.e. with that part of the image in focus, there would be the same colors and shapes there, just not blurry).

Hopefully that helps, hopefully someone more knowledgeable comes around to clarify, and I apologize to any photographers out there for mangling your trade.

the horizontal line type of lens flare is indeed an effect on a type of lens

i believe post #1600945 also falls on lens_flare. that artifact can be achieved in photography by using a cross screen filter - particularly a 4-point star filter. and this is common in eyecatch /ttgl

the reflections on jewelry (or swords or metals), i think would be better tagged as glint though.

i've been using bokeh since it was introduced to me. my hint on this is when light sources are out of focus (depth of field). post #1568447 is an example.

of course there are technical details i might be missing.