See the tag wiki for depth-of-field: https://photo.stackexchange.com/tags/depth-of-field/info. This has a relatively in-depth article explaining the term. On the other hand, the new SE blog post about tags and tag wikis talks about tag wikis mostly in terms of defining what the term means to the community, and how it should be used here.
Should articles like the above be actively discouraged?
There's a difference between the tag wiki and the tag wiki excerpt.
The excerpt needs to be ~400 characters of awesomely succinct plain text; the full wiki has no such length or style limitations.
Still, I do think it's important in both cases to begin with "what does this tag mean to your community" first, as in:
which questions should have this tag, and why?
Because, let's face it -- people can get a definition of the depth of field effect in a lot of places. What they can't get, however, is guidance and advice on usage of this tag in your community.
When choosing a tag I want a quick answer to the question 'Is this the appropriate tag?'. At that stage I really couldn't be bothered with reading a full article.
