Per ISO 1222:2010,[1] the current tripod bolt thread standard for attaching the camera calls for a 1/4-20 UNC[2] or 3/8-16 UNC thread.[3] Most consumer cameras are fitted with 1/4-20 UNC threads. Larger, professional cameras and lenses may be fitted with 3/8-16 UNC threads, plus a removable 1/4-20 UNC adapter, allowing them to be mounted on a tripod using either standard.
Historically, The Royal Photographic Society recommended the thread standard for attaching older cameras to tripods was 3/16-24 BSW (3/16 inch nominal diameter, 24 threads per inch), or 1/4-20 BSW[4] for smaller cameras and 3/8-16 BSW[5] for larger cameras and pan/tilt heads. In this application, the BSW and UNC thread profiles are similar enough that one can mount a modern camera on a legacy tripod and vice versa. The UNC threads are a 60-degree angle and flattened, whereas the BSW are a 55-degree angle and rounded crest. However, at least one English manufacturer uses No.1 B.A. (British Association) for its tripod mount thread.