For photographic lenses, I'd say go ahead and write an article at photographic lens and we'll just add links from lens and lens (disambiguation). I'm assuming that you'll want to write photographic lens from a more practical point of view, and keep lens mostly as a theory of optics type article. Alternately, we could just make lens a disambiguation page, and move the articles to lens (optics) and lens (photography). I don't have a strong preference, although the first option is easier.

As for rainbow, I can't see anything wrong with the picture - what makes you think it is a fake? It seems it was added by user:Karen Johnson, BTW.   20:43 Jan 23, 2003 (UTC)