Fixed expression only applies to certain elements. The part of firework shows and light shows that comes under copyright is the Industrial Design. Thus the expression of that industrial design is wholly protected. If I photograph a pattern in one of these shows, I can't sell the recognizable pattern that has been copyrighted by the originator. A fine line, but as I mentioned before, greedy people. Besides, if I design a light show, I don't want someone copying even portions of it in such a way that it could be reproduced. Fair use for advertising or publicity yes, duplication no.

Further more, these live performances have related laws regarding rights to record or reproduce that have nothing to do with copyright that prevent their being documented.

Live theater has long as a condition of performance rights to a work, included prohibitions on recording or mechanical reproduction (meaning traditional photograph).

Copyright is a fascinating area and its basics are very straight forward. The devil is in the details of each situation.

I've been photographing architecture and building for over twenty years and there are jurisdictional issues as well. When extra-legal entities like associations, districts, and authorities kick in, the laws get wild. We have park districts where you will rarely see any photography of structures as the 'live' view is meant to be part of the selling point of the experience. To commercially use photos of these buildings require permissions which are rarely granted. There are some private architectural parks in the southwestern portion of the United States where there is no real public access, but they are considered public places but there are restrictions as a condition of that access.

I have architectural photos of several major sports stadiums take during construction as a result of work I was hired to do. But the moment the building was completed from the contractors legal point of view, I no longer could photograph for commercial purpose the interior. At that point it wasn't a public place as it had not been opened to the public. And the public has never been allowed access for purposes other than that they have been ticketed for. One small example.