I would proceed with caution, but you likely have some options. I am hesitant to tell you to file a claim today as word spreads as far as who has a reputation for rocking the boat, and this may have an effect on your ability to get more work from the same label, producer and other people in the industry.
First, you need to refresh yourself of the terms which you agreed to shoot the footage. A discussion and understanding between you and the producer could constitute an oral agreement to be paid if money was discussed. It would also allow for a lawyer to understand whether the footage you took constitutes a work-for-hire and the lawful property of the producer/label.
Second, you need to make a demand for payment in writing, if compensation is owed you pursuant to the contract or if there was an understanding that you would receive customary compensation.
If things get nasty, you can file a suit for compensation if there is an understanding that you would be paid. This should be done professionally with the intention to affect your reputation in the least. I strongly caution against posting footage on facebook/twitter as you're going to incite people as opposed to encouraging them to give you what you need. You may also cause damages to the label/producer that far exceed your claim for compensation.
It sounds like you cannot afford NOT to speak with an entertainment attorney. You may possibly be entitled to money that the attorney may be able to help you get, and you may be needing to defend a lawsuit based on the cease and desist letter. You should at least meet with a few to see what they say, even if they charge a couple hundred dollars for the consultation, though I imagine many, if not most, would offer you a free consultation. If you need a referral to a good one feel free to contact me via e-mail or phone and I will get you his contact info. Good luck.
Michel & Associates, PC
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This is terrible - there is nothing worse than having your creativity taken advantage of by others for profit, and not getting your share of it. So sorry you are going through this!
I also think you need to speak to an attorney right away - a number of attorneys offer "contingent fee" arrangements, meaning that you do not pay them unless you win in the lawsuit. You may have intellectual property rights in the video, especially if there was no written contract. Copyrights of authorship, as you know, arise automatically. Further, in situations where there is no written contract, or an oral contract, you may be entitled to "quantum meruit," which is, the reasonable value of your services.
There are plenty of good attorneys on this site and others. Speak to several, evaluate your options, and hire the one that you feel most comfortable with.
If I can be of help, please let me know. I have litigated non-written agreements before, and my firm offers contingency fee arrangements. I will be glad to discuss the specific facts of your case with you (consultations are always free).
Take care, Rabeh
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As my colleagues noted, you clearly need an attorney. The fact that you directed this video without a contract, makes it difficult for you to prove what your payment rates were, whether you even WERE the director (as opposed to a producer, grip, associate etc.) The fact that they want the hard drive is your leverage at this point. Seek counsel immediately.
The author is a Maryland attorney; however no answer given on Avvo is intended as legal advice or intended to create an attorney-client relationship.