I think that The Black Sleep had some "exploitation" success, as it was heavily promoted at the time. We're not talkin' The Ten Commandments or Ben-Hur here but respectable box-office, good bang for the buck for the producers. Also, its release more or less coincided with the Shock Theater package of old horrors being syndicated to local TV stations, and so it probably hung around in the theaters longer than usual for a black and white programmer. A most unusual film to come from Hollywood in 1956, with its Victorian look and cast suggestive of the 40's more than the atomic age.

Not having even glanced at Castle's autobiography in ages I can't recall what inspired him to turn to horrors in the 50's. Macabre, I believe, predates even the Hammer horrors, so Castle was off and running before those bigger films hit, and Macabre made money. Surely the success of Shock Theater was not lost on Castle, and may have been a determining factor in Castle making his films in black and white, so as to suggest classic horror in tone, in setting, which his movies did, and yet offer viewers a more contemporary kind of entertainment, set in modern times, with a Halloween party mood on the side. It always seems to me that Castle's films are winking and nodding (to the extent that a movie can) at their audiences, as if to say "let's not take things too seriously".

Hammer's films are a different kettle of flesh, and I wonder if their success in the States was Shock Theater-related or was just gonna happen. Their pictures are at their best good enough to play as stand alone movies without having to be sold as horrors. It's easy to guess the target audience for a Castle horror when watching it, while the Hammers are enigmatic in this respect. At times they feel like David Lean or Powell & Pressburger horrors, with their vivid color, artistic touches, classy actors, more intelligent that usual dialogue. Roger Corman followed on the heels of Hammer in using color and good actors, seemed often to be aiming for the same audience as Castle, to the extent of appearing to dumb down his movies so as to play to the lowest common denominator. A bit harsh on Corman perhaps, but true in my opinion.