You will find many "3D SBS" files online that are 4-8GB in size. A 3D Blu-ray ISO is typically . The difference is night and day.
In many jurisdictions (notably the US under the DMCA), it is to rip a 3D Blu-ray you physically own to an ISO file for personal backup and archival use. It is illegal to break the encryption (AACS) for a disc you do not own. 3d bluray iso download