Ah, but Sturm I'm picking nits here and you can't just wave your hands like that :)

"this whole thread started as a lighting question"

No, it started as a shadowing question.

Nebula's original posting said:

"My desire is to do some backlighting of a character to get a shadowy outline"

It was you, Sturm, who first talked about silhouette:

"If you just want a silhouette that's another thing sorry I don't watch Bond movies so cannot relate to your example! :)"

But as I said sometimes a shadow is a silhouette, and sometimes it's not. But when the shadow is a silhouette, then by definition the silhouette is the shadow. In this case the shadowy outline was indeed a silhouette, and it is what was asked for.

I understand that you can set up a situation where the background scene behind some characters is so much brighter than the characters themselves, that they end up forming silhouettes on the film if you set your shutter speed up high, and that these silhouettes are not shadows. Yes there are other kinds of silhouette. What exactly is your point? My point is that when a shadow forms a sillhouette, then that shadow is called a sillhouette.

I'm objecting in particular to your obfuscating phrase "strictly a shadow, and not a silhouette". The set of all possible shadows and the set of all possible silhouettes have a non-empty intersection. The scenario we've created here is one where the resulting image is both a shadow and a silhouette at the same time. It is not meaningful to make the statement you made.

Are you just trying to confuse people? This issue is important to me because I constantly run into people on Rendo who use words they don't mean, and the conversations get very confused. People talk about, for example, the surface facing away from a light source as being "in shadow" but it's not in shadow. Being in shadow means that the surface would be receiving and reflecting light from a light source, but that some other object in between is blocking the light. See what I mean? And yet these people think the unlit side is a shadow and are trying to adjust the brightness of this surface by manipulating shadow parameters.

This is why I care - because being imprecise about the words results in imprecise thinking. I am trying to correct the precision by which we use the term "sillhouette" - it is an effect resulting in a solid (no interior detail) shape against a light background, said shape being clearly the depiction of the outline or cross section of some real object. The term in itself has nothing to do with light, despite what you may think. However, light and shadow are capable of creating sillhouettes. 

Am I clear now?

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)