Cinematography-Theory-And-Practice

Lighting for Bluescreen/GreenscreenOptimum exposure levels depend on the nature of the subject andthe setup. (Figures 16.2 through 16.8). In general, you want theexposure of the background to be about the same as the foreground.There is no general agreement on this. Some people set them to beexactly the same, some people underexpose the background by upto one stop, and some people light the background by as much as onestop hotter than the foreground.The bottom line is simple: ask the person who will be doing thefinal composite — the compositor or effects supervisor. Different visualeffects houses will have varying preferences that may be based on thehardware/software combination they use. Always consult with youreffects people before shooting. This is the golden rule of shootingany type of effects: always talk to the postproduction people who will bedealing with the footage: ultimately they are the ones who are going tohave to deal with any problems.Lighting the background can be done in many ways using tungstenunits, HMIs, or even daylight. Kino Flo makes special bulbsfor lighting backgrounds; they are available in both green and blue(Figure 16.2). Figures 16.4 and 16.5 show Kino Flo’s recommendationsfor using their units to light a background.Set pieces (such as tables, boxes to sit on, etc.) that are painted togive the actor something to walk behind or interact with can presentproblems. The top of the piece will sometimes be hotter than theshadow side. This will definitely cause problems with the composite.Lighting can help, but it may create problems of its own. One trickis to use paints of different reflectances on the top and side surfaces.Nothing will undermine the believability of a composite morethan a mismatch of lighting in the foreground and background plate(the scene that will be inserted in place of the greenscreen). Carefulattention must be made to recreating the look, direction, and qualityof the lighting in the background plate.Figure 16.2. Kinos used to light alarge greenscreen in a water tank.(Photo courtesy of Kino Flo.)technical issues313