Lang looks at a photo of the cityscape of Metropolis.

FRITZ LANG: We constructed a miniature set of the streets about seven or eight feet long, in an old studio with glass walls and we moved the little cars by hand, inch by inch, one frame per movement, filming image by image. We moved the planes and photographed them in the same way. This scene that takes only one or two minutes on the screen took six days to shoot! Ultimately the worse difficulties we encountered were not in the shooting but in the lab. The cameraman had told the technician to develop the film normally. But the head of the lab, knowing the time we had spent filming this short scene, decided to develop it himself. No one had thought it necessary to tell him that for reasons of perspective, the cameraman had filmed the background a little out of focus to give the impression of great distance. The head of the laboratory started to develop the negative focusing the background and not the foreground. The scale of dimensions was then destroyed. I tried to keep my calm. “These things happen, my children,” I said, “Let’s start again.” And we did. (The first thing I discovered about making films is that you never make them alone. Your crew helps you. And I had a remarkable crew.) As for the videophone scene, it was done by projecting a part of the film shot previously in the rear of a telephone apparatus, across a translucent screen, one foot by two. This was the first rear projection and the first transparency. We didn’t realize the importance, the scope of what we had done, for if we had we would have made a fortune patenting a process universally employed today. At the time we only knew that there was a problem that had to be solved. My cameraman, Gunther Rittau, was determined not to fake the shooting; he used his intelligence to arrive at this solution: he synchronized the camera with a projector that was to project the picture of a man on the videophone. That was done with linked rods connected by mobile joints going from the camera to the projector, which were, because of the shooting stage, rather far from each other. Then, when the scene started, the two machines worked at the same time in perfect synchronization. The flooding of the workers city was real, shot in normal scale. Hoses at street level projected water like geysers.

The robot, galvanized by Rotwang's scientific machinery.

Another camera effect concentrated on creating the robot Maria. The concentric rings of light that surround her and move from top to bottom were in fact a little ball of silver rapidly turning in a circle and filmed on a background of black velvet. We superimposed those shots, in the lab, over the shot of the robot in a sitting position that we had filmed previously.
The city lit up at night was done with an animated drawing. The way we filmed the explosion of the heart machine was one of the first uses of the subjective camera, giving the audience the same impression that the actors feel of the shock. The camera was attached to a swinging pulley on a vertical board that advanced toward the machine on the platform then moved back to give the effect of the explosion.
Sergei Eisenstein visited me in the studio and we had a controversy about the moving camera versus the fixed camera, but we weren’t able to discuss it for long because of my shooting schedule. I planned to see him several days later, but he had already left Berlin and I never saw him again. Someone told me that he did a study on my working methods on the first Dr. Mabuse, which I’m told was published in Russia.
Speaking of camera effects, there are some that can only be done thanks to make-up. For example, in The Testament of Doctor Mabuse, when Doctor Baum meets the ghost of Mabuse at night, he sees on its head the living brain he had dissected that very morning, in order to discover what anomaly had made Mabuse a great criminal. This is how it was done: we had a special skull on which we put glass tubes outlining the form of the brain. The tubes were filled with mercury so the liquid moved whenever Mabuse did. Between the glass tubes the make-up man put bits of white hair, like Mabuse had in real life, which gave the public the impression of seeing his brain through the skin. To enhance the horrible aspect of the spectre, a bit of eggshell was placed over each eye and the cornea was painted in a deformed way.