Virtual light source • Known Methods and Practices

Example 1: 

To light interiors of a high building, beam projectors are placed on street level, shining straight up. Large, hard reflectors placed overhead of the windows redirect the incoming light and simulate incoming natural daylight. Because we create a virtual light source way up and high in the sky. 

We add the distance from the light fixture to the reflector, and add distance of a virtual light source way behind of such a parallel beam light fixture. The effect is a light that is placed very far away, thus minimizing the effect of the inverse square law. It allows actors to move freely, without any noticeable change of light intensity and creates a “natural” light.

 Since the special optical system of the dedolight allows for a very narrow exit angle, down to 4°, the virtual light source results from the elongation of the outer rays, and where those cross, the virtual light source becomes active.

Example 2: 

On a film that I shot in the early 1970s in Indonesia, I had to film inside large housings which had rooftops, reaching very far down.  

Since in such large (communal) housings the people live on a raised platform, I was able to acquire a considerable number of table-tops, which I fitted with broomsticks on a hinge. I covered these table-tops with a very lightweight reflective material from Rosco (Rosco Flex). There was even a special glue to attach such a reflective material to pretty much any surface (Rosco Bond). Thus, I was able to create with a small budget an efficient multitude of very hard mirror-like reflectors and many other reflectors with a crumpled surface, producing a more dispersed reflection, softer and gentler light that would spread wider. 

Placing these table tops at angles all around the building, I was able to reflect the sunlight towards the interior ceiling. 

In addition, I covered these interior ceilings with more of such reflective lightweight materials, thus reflecting the reflected light into a very gentle but still controlled and variable way onto the action area in the center of the living spaces.  

That worked very well. It was simply necessary that my assistant would step out every once and again to re-direct the reflectors as the sun was moving, but since near the equator the sun is friendly enough to stay for a long time very high up in the sky, the re-adjustment was easy and quickly done.

Example 3:

In one of our tutorial videos, the British DOP Ian Murray shows how a hard reflected light becomes polarized, and he holds up his hand and shows how the impression and the narrative of the skin on the surface of his hand is changed by the polarized light, generated by the hard reflective surface. 

Everyone of us can add a variety of other examples, including the common practice of using bounceboards, bead-boards, styrofoam surfaces and such.