Working with some folks new to the business and I myself have never worked on credits for docs.
How much detail is required for these photo/video credits?
I was going to copy and paste an example but one photo credit alone is almost 12 lines of text :P
My experience is mostly features and shorts.
There we do the basic "Stock Photography by GettyImages".
What's the legal on this and where can I get more information?
I have been working for 3 years on cultural documentaries for my government. I have to add a lot of people to the credits who were not even part of the production process but have political authority. So the end credits end up looking ridiculously long. Funny thing is this gave me an oportunity to get creative with the credit design. Since we talk about history and archeology some times I place the credit over an old map or an antique code, sometimes I place it over pictures of the crew working, or animations of some sort. People love it, they don´t mind the credits being so darn long.
No legalities unless using other companies' sources. It's up to the director. Sometimes I get quite lengthy and sometimes I don't have so much as name keys in a piece. That's what I love about docs. There is no template whatsoever.