Photo Mode and House sequences are unavailable when playing in co-op mode. Tethering will keep you bound to your co-op partner. If the joining player strays too far away from the hosting player, they will be translocated to the host. If one player is Downed and the other player gets too far away, they will get translocated to the Downed players. Additionally, if one player triggers a Lockdown while the other player is not there, the latter will be translocated to the Lockdown room.
Co-op sessions last until the end of an Act (or until either player decides to leave co-op)