I was hired by DreamQuest Images to paint several matte paintings of the Hilton Hotel on Mars. We used a dual IP process. The mattes were painted on glass, with a background miniature element composited in. The plate was bipacked against the IP. Painting to IP stock was a challenge because the film "saw" color in an unusual way and you had to understand what your color would turn into when exposed directly onto this film stock or you couldn't make the process work. Your painted color changed RADICALLY.