In this day of digital transformation of images and sound and the haphazard distribution of audio-visual material on the net it is critical to make sure that all material used in a tape is used legitimately. This subject is extremely complicated and is frequently discussed on the net. One good site regarding copyright issues in the US is the Copyright Website at http://www.benedict.com/. In theory the issue is simple: all graphics (including fonts and map bases) and sounds must either be entirely your own, out of copyright, or used with permission of the copyright owner. Period.
Some people seem to consider that because material is available on the net it is free for any use. That is simply not the case. You may get away with using such material for your own private purposes but when you start publishing or broadcasting that material, you are letting yourself in for legal problems.
Even material that you buy, such as some inexpensive sound effect CDs, typically have strict use restrictions on them. If you buy sounds or graphics to use in your production make sure that the rights you are buying are the rights you will need for your production. Remember fonts are subject to copyright too! Are you using any shareware fonts you haven't paid for? You had better pay the fee before you publish!
Most natural subjects that you record yourself are probably safe, but keep in mind that certain natural subjects may be subject to forms of copyright protection. For example certain animals that are recognisable as specific individuals and are owned by people may be subject to copyright and you may have to obtain permission to use footage of these animals for certain uses. Certain areas, e.g., clearly recognisable lands in private ownership, may also be subject to some form of copyright protection. This is a complex and evolving field and you are well-advised to seek local legal advice if you feel that you have a potential problem. Sometimes the copyright issue is not a problem because of the use you are putting the footage to. News items for example are often less subject to copyright restrictions. However it is not as clear when documentaries are concerned. Advertisements are of course the type of use where copyright authorisations are most important. Indeed clients for advertisement footage typically require extensive releases to be signed by any recognisable individual or subject.
Finding out of copyright material can be difficult. Rules for copyright duration vary from country to country. Often the length of the copyright may be some time (e.g., 50 years) after the death of the author of the work. This may not be easy to determine and may be quite different from the age of the work itself. How about an Audubon print? Surely that is out of copyright? Yes, and if you are fortunate enough to have such an original print you will be able to copy it and use it in your production. But can you legally copy an Audubon print from a new book you just bought? Probably not! After all somebody had to photograph the original prints and that person now holds the copyright to his or her photograph of that print. At least that's how we would interpret the situation. You may want to check this interpretation locally if it is of concern to you. We're not lawyers but we've tried to keep up to date on copyright issues of concern to us.
In a word be careful and don't take copyright and releases for granted!
A related issue worth keeping in mind (although it is not really an ethical issue, but we didn't know where else to put it!) is the question of getting permits to film in certain areas. The issue of permits for professional photography or videography on US public lands has been a topic of a lot of debate on the net and in Congress and it appears not yet fully resolved (check up on the NANPA site at http://www.mcs.net/~rjacobs/nanpa.htm for updates on this isse). In other countries there may be very strict permit requirements or even total prohibitions to taping in certain areas or certain subjects. For example in certain European countries there are strict prohibitions regarding photographing certain protected species. Aerial photography may be subject to special permits also.