Flash photography of any sort is distracting and annoying to patrons, and is prohibited without permission. Use of any camera equipment, including digital cameras and video camcorders, may not be used without permission of the library. Photocopying The fact that some materials are light-sensitive and can be damaged with even a minimal exposure to high intensity light, is ample reason for your caution. Newsprint, telephone directories, and city directories were printed on papers that were never intended to last for a long period of time. Manuscripts and other documents may have been written using light-sensitive inks that may easily fade until the writing is indistinguishable.
Some books fall into both of the categories.
If you have any questions about copying these fragile and ephemeral materials, don't hesitate to ask the library staff. You don't want to damage any materials that future generations might otherwise be able to enjoy. Some libraries have compiled collections of video and audio tapes that relate to genealogical research. I have seen some impressive videotapes about using maps in genealogical research. I've also borrowed audio tapes of books and presentations of a historical or genealogical nature.