Russell Crowe agreed to do the film with Joel Schumacher when the film was slated to be a "dirty, handheld gritty thriller." Crowe had one stipulation to all this and it was the scene where his character is looking at the kiddie porn and throws it in the trash. He throws a cigarette so it would start burning inside the trash can. Schumacher agreed. Then out of the blue, Nicolas Cage's agent called Schumacher and told him that he wanted to do the film as well. Schumacher then contacted John Calley at Sony and told him that they could do the film with Crowe as a "low budget, dirty handheld camera thriller" or a much bigger film with Cage. Calley then agreed to do the film with Cage as the lead which eventually led to a much bigger budget. Schumacher realized Cage was right for the part when Cage reportedly told him, "I want to play a role I can internalize instead of my normal schtick."
The actress (Jenny Powell) playing the character of Mary Ann Mathews was originally a stripper hired to act as a stand-in. Joel Schumacher gave her the part of the victim on the 8mm film as she had a suitably "haunted" look about her.
The film's production encountered concerns regarding the dark subject matter, and the studio asked Andrew Kevin Walker to lighten the film's tone. With Joel Schumacher as director, Walker felt a rewrite would no longer be needed. As it turned out, Schumacher supported the studio and made changes of his own, leading to a much-publicized fallout between the two, with Walker virtually disowning the film and walking away from the set. He refused to even watch it.
The location of the final battle between Tom and Machine was a great place to shoot, according to Joel Schumacher, because the neighbors and owners of the house were very hospitable. In turn, Schumacher gave them signed posters of his Batman movies, and t-shirts and assorted gifts for their hospitality.