In cinema it works the same as in software engineering. There is an exception to normal copyright law where works made in the course of employment are treated as if the author is the employer rather than the actual author of the work. Its known in copyright law as a "work for hire" https://en.wikipedia.org/wiki/Work_for_hire

> In the United States, United Kingdom, and several other jurisdictions, if a work is created by an employee as part of their job duties, the employer is considered the legal author or first owner of copyright.

> It is an exception to the general rule that the person who actually creates a work is the legally-recognized author of that work.

So then a film project where no one is paid would need all operators to cede their copyright to the person spearheading the project, correct?

If employment is an exception, I wonder what would happen if an animal that you owned pressed the shutter on a camera.

Not paying anyone would be a violation of minimum wage laws. Or it would mean they are truly equal partners in the project who have no "employer" they are working under. In which case it does seem most fair that they would all own the copyrights to their contributions absent some other agreement to assign copyright.

> A director who is the creator of the project must have to get rights from every camera/mic operator.

No, because they're already paid to do that job. And a director is paid too - he doesn't have any copyright for his work. The employer does.