After principal shooting in April and May 1979, Carpenter and his editor Tommy Lee Wallace began to piece together the movie. To their horror, both agreed that the film "was a disaster. Quite simply, the picture didnít work". Carpenter stated that "This was the lowest point I had come to in my professional career." After a massive effort they rewrote, rescored and re-cut the movie in one month, after which it was a great success.
John Carpenter reportedly shot additional gory scenes after the original 'PG' version failed to impress the preview audiences. The extra scenes were then inserted which then earned the film its 'R' rating.
After a rough cut editing, the movie appeared to be much too short for a theatrical release (about 80 minutes), John Carpenter subsequently added the prologue with the Old Captain telling ghost stories to fascinated children by a campfire.
Some years ago I watched the fog on tv, at the end of the movie, when the pirates come back to the church, the last scene shows the pirate swinging his sword towards the priest, then silence. The version I watched showed the head of the priest falling from the air and landing on the ground then the movie ends.