> Wait, but then if I hand my camera to someone and ask him to take my picture, I don't own the copyright of my own picture!

Yes, that is correct. Copyright resides with the person who provides the creative expression in taking the photograph, not in the subject or person who provides the equipment.

This most often comes up in the context of portrait photography/family photos. People expect that they can automatically make copies of the pictures of themselves that they paid someone else to take, but unless the contract is specifically written and signed by the photographer that the work is a "work for hire" and specifies that the copyright is owned by some other person, the copyright remains with the photographer.

In a theoretical sense, probably not. It's not a work for hire. You probably gave at most vague directions about how to compose the photo. The fact that it's your camera is irrelevant.

Meanwhile in the real world I somehow doubt that this has ever come up as a legal issue.

Maybe this is why selfies have become so popular... One could imagine a scenario where copyright trolls would hang around in popular tourist destinations kindly helping people take photos then sue them once the images end up getting posted on social media...

Wait, does that mean you don't own the camera nomore neither?