International projectionist (Jan-Dec 1956)

center (let's call it the line of no distortion) may vary in its position due to the projector-screen setup or other factors peculiar to the process in which we are working. This line of no distortion could easily be above or even below center; so photographic tests similar to the one described above are advisable. Correcting Distortion Now suppose we were to repeat the same test but instead of photographing the lines straight on we shoot them at a % angle. We will find that the bend will hardly be noticeable and certainly not objectionable. The greater the angle from straight on, the less the lines will bend. (Fig. 4). From the foregoing we can see a number of ways to help ourselves when we wish to use an extreme wide-angle lens on a scene containing pronounced horizontal lines. The most obvious, of course, is to keep horizontals in the center of the frame or wherever the line of no distortion happens to be. Unfortunately this is not always possible or desirable. A less-obvious but often simple solu FIG. 2 — Example of well-placed camera setup for wide-screen photography. Here distortion of the straight lines of the highway is minimized by shooting at a three-quarter angle. center of the frame, but the near curb ran across the screen in a pronounced curve, making a rather strange looking road. We blocked the benches up slightly to cover the nearby curb, and, leaving the center bench straight, we angled the outside benches toward the camera. tion is to set up the camera so that the prominent lines in the scene are bent in the opposite direction, so that on the screen they will appear straight. When thinking in depth, it can be remembered that horizontal lines off the center bend back into the screen, therefore, these lines should be bent forward (toward the camera) an amount determined through the ground glass. (Or, on paper, if it is a question of set design.) I worked on a picture recently in Cinemascope in which it was necessary in one setup to use a 35-mm lens. The scene was a building with a roadway running straight in front of the camera, and the tops of three park benches in the foreground. The far curb of the road ran straight and was close to the FIGURE 3. How horizontal lines are bent when scene containing them is photographed straight on with extreme wideangle lens. When seen on the screen, the tops of the benches ran reasonably straight and parallel to the opposite side of the street. Where possible, the easiest solution in a case of this kind, is merely to change the setup so that any lines in the upper or lower part of the screen become diagonals. In the scene just described, had it been possible to move the camera so that it was three quarters, to the road, we would have had no problem. Tricks with Scenery Still another possibility — and one we had to resort to often with Cinerama— is to break up these lines by blocking them at some point. A floating piece of shrubbery is ideal for this — anything that will keep the eye from seeing the full length of that bent line. Of course, many lines look perfectly all right if they bend. A railroad track bending through the bottom of the screen may look perfectly natural, except when the train comes through and the cars bend in the middle! If we repeat our line distortion test with vertical lines instead of horizontals and tilt the camera we will see the second basic distortion. The center line {Continued on page 32) FIGURE 4. When the same scene is shot with the camera placed at a threequarter angle, the horizontal lines are bent only slightly. INTERNATIONAL PROJECTIONIST • JULY 1956 17