J6I
From Just Solve the File Format Problem
J6I is a format used in Ricoh digital cameras, and was once in common use, though not any more. It is one of the many formats for which any attempt at a search for details results mostly in scads of the cookie-cutter sites that sprout up like kudzu to "document" every file format, but are exceedingly short in actually useful information. By putting this page here, we've probably added one more not-so-much-information page to that bunch, but at least it's a wiki so that if you do happen to have a bit more to say, you can edit it yourself to add it and help future information-seekers.
The format is apparently related to JPEG, but given some proprietary twists.