Oh goodness. There was an interesting discussion of the copyrightability of fonts on this list a few months ago. On Sat, 16 Mar 1996 19:26:41 GMT, Terry Carroll (carroll@tjc.com) wrote:

The rule against copyright protection for typefaces comes from the Copyright Office's position that a typeface is purely a design for a useful article, and is not a work of authorship. The Copyright Office successfully argued this position under the 1909 Copyright Act, in Eltra v. Ringer, in the 4th circuit in 1978. In 1992, it codified its position as 37 C.F.R. 202.1(e).

And despite a valid distinction between fonts and typefaces, both seem to be unprotected (except for such things as Postscript fonts which are actually programs for expressing typefaces, rather than mere data).

Terry's article "Protection for Typeface Designs: A Copyright Proposal" in volume 10 of the Santa Clara Computer & High Technology Law Journal, would be good reading for the photographer, before the shutter is actually opened on the window lettering. It is quite conceivable that elaborate and decorative letterings (like the fancy letters which begin chapters in old books) might transcend the functional and utilitarian purposes abandoned by the Copyright Office. Alternatively the phrase(s) created in that lettering may be the name of a store, and again, subject to trademark law, or even an original authorial and hence copyrightable expression.