Chapter 12: So You Don’t Have a Million Dollars
Figure 12.12: Finding camera position by using scale calculations. If you block off the bottom half of the diagram below the background plate floor, you will see where the camera was placed to shoot the background. For the projection composite camera position use the composite floor as a reference, and you can see how everything is scaled up along the vertical lens angle.
coincide with the lens of the projector. Beyond this arrangement was a Scotchlite screen. Since the background was shot using a level camera, the composite camera was set level as well. As far as matching lenses, I took some liberties and positioned the actress and focal length until the image looked correct to my eye. To do the shot by the book, I would have measured from the floor to the center of the lens in the background camera, arriving at 2 inches. If I had assumed that the actress, Amanda, was 2 inches tall and I made the scale 1/3 inch to the foot, then I would have placed the composite camera 6 feet above the floor when I shot the projection. The screen would be positioned so as to fi ll the camera with the background image. As far as the lens goes, I may fi nd that the background camera has a different size chip than the composite camera, so to match the lenses I need to consult a lens lookup table. If the background camera has a 2/3 inch capture chip and I shot with a 27 mm focal length lens, I would have a 35 degree horizontal angle of view for a 1.33 presentation. If the composite camera I use has a 0.5 inch chip, I go to the lookup table and find that for a 0.5 inch chip to give a 35 degree horizontal angle of view I will need to use a 20 mm lens. (Refer to the lens angle table found in Chapter 9.) Since the composite camera in this demonstration did not have convenient focal length markings, I positioned the lens by eye. I mention the different size capture chip for those who might face a situation in which the background camera and the composite camera have different-size chips and yet have the ability to adjust to an exact focal length. One method of aligning the projector and camera lenses is to place a scrap piece of Scotchlite on a flat surface positioned in front of the Scotchlite screen in the subject
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