Public domain and footage have some of the worst nightmares for any documentary filmmaker as getting the footage for free can be a chore. in public hand can create an ad and later entity liable for the footage. It is important that one looks out for things that are copyrighted which have been expired. There is a lot of 2015 US public domain and copyright term for the current laws, which is governing when the right expires. Make sure that you have public footage which can be hard to get a copy for free. Also, there is a fair use warning which allows you to use for a certain timeframe, etc. Generally, two reasons that one has to pay for when they are looking for the pay someone which allows you to find it, transfer it and then ship it. There are many great sources out there can give you free footage from public domain footages for your documentary.
Pond5 Public Domain Project
Pond5 Public Domain Project is one of those who has a project in 2015, which is something that one can do to create a free account that can start downloading. This public domain is trying to make this content available which is trying to keep the content available for our customers and contributors without any change. There is a designated team who will help you find the right videos without the having to deal with the copyright restriction over the content that has been produced.
Prelinger Archives housed at Archive.org
Prelinger Archives was founded in the year 1983 by Rick Prelinger in New York City. They have over 60,000 ephemeral which remain in existence trying to hold almost 11,000 digitised videotapes and titles. They are trying to grow and are collecting and preserving these films in the historical significance which have not been collected from elsewhere. There are many internet archives which do not have to get the written permission to use any material and allows you to have the right repurposing use.
The Internet Archive Moving Images Archives
Anyone can upload anything that The Internet Archive Moving Images Archives produce on the internet and also add a lot of copyright status even when they have listed it as a public domain and was uploaded by discerning. There are many companies which have digitised these movies allowing them to have easy access to the rich and fascinating collection. There are many unrestricted access to these films which hopes encouraged the widespread use of the moving image in the new context as they can upload them to make better use of them from before.