I think copyright and usage rights are two different things. You can retain copyright but allow use based on your agreement with each client. If a client contracts you specifically to do a job then he's probably going to want to know that the footage he's buying is purely for his use. The price you agree with him will therefore include right of usage of the footage. If you are simply capturing footage to later sell or use within a non-specific video project then that's a different matter. You could sell that as you wish. As to the commercial issues, your fees are incredibly high, I've seen day rates here in the UK of around £800 (although I'm sure some people earn more or less depending on the subject / risk etc) so well done on that. What type of contracts are you mostly selling?
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