Sid Terror wrote:

Disney had the rights tied down and were the only ones legally allowed to use the sodium technology in North America... Which is why Harryhausen had to go overseas when he wanted to use it.

I'd heard from one of the old guys in the optical department over at Disney that the company only owned two sodium optical printers and one of them had a lens with defects.  That left them with only one of them that they could count on for over a decade.  The Disney company babied their one good optical printer for years, even cannibalizing parts from the other one to keep it going,  Finally it just became too financially stressful putting all their eggs in one basket and they said "Aw, the hell with it!" and moved on to other technology.  ...Or so the story goes as he told it.


  

As I heard it, the prisms used as beam splitters in the cameras (which created the original footage and the matte simultaneously) were so precise and fussy that only Disney and Rank had any success with them. I think it was more a technological than a rights issue.