The Front-Projection Process of Composite Photography
The development of a new screen material by 3M (Scotchlite 7610) has made possible the Front Projection Process, in which those portions of the projected image falling upon the actors are not visible, and shadows cast upon the screen by actors and foreground objects are not seen by the camera. The beaded Scotchlite screen is a reflex reflector, returning most of the reflected light back to its source. Gain is sufficient for one footcandle of background image intensity to balance a 200-fc foreground illumination. The very low illumination required by the Scotchlite screen makes possible background screens as large as 30,000 ft2 when using an arc projector. The practical use of front projection requires careful alignment of the camera and projector lenses to superimpose their front nodal points. The paper provides tables that define a safe minimum object distance as a function of screen distance, lens focal length and ƒ/stop. Panning and tilting of the camera to follow action is permissible in front projection if the front nodal points are carefully aligned. By observing the limitations of the front-projection process, excellent results have been obtained. The paper explains these limitations and provides an operations check list.
- Print ISSN
- 0361-4573
- Published
- 1971-09
- Content type
- Original Research
- DOI
- 10.5594/J05742