BOLEX S-221 Technical Information download pdf (Page 18)

Optics and Cinematography

Part of the magic of film is that it simplifies visual experience. This is particularly evident in its inability

to portray subtlety of tone. The heightened contrast emphasizes the role of light carving a deeper

impression in the psyche.

The decisions of a cinematography revolve around the use of light. Whether starting from scratch

with artificial light fixtures in a studio or chasing a profound moment of natural light in the field, an

awareness of the underlying principles makes the decisions more engaging.

Coherent Light

There are two basic formations of light energy: coherent and diffuse.

When light is generated at a point source, energy is emitted uniformly in all directions. This is

sometimes imagined as many "rays" of light "moving" away from the source in perfectly straight lines.

The further the rays travel from the source, the more similar in direction their paths become. The

further light travels from its source, the more parallel, or coherent the “rays” become.

As the distance from the source increases, the rays become more parallel-like.

Assuming that the light passes uninterrupted, this "parallel-like" nature, or coherency, is responsible

for producing shadows with sharper edges. Note that the shadows are sharper when formed at a

greater distance from the light source.

Less sharp shadow

produced nearer

the Light Source.

Shadow is sharper

when the object is

a greater distance

from Light Source.

Creative Use of Coherent Light

Shadows and texture. Coherent light is excellent for forming deep, pronounced shadows on 3-D

objects and enhancing texture on rough surfaces. Surface textures become even more evident

when the light is raked-- or directed along the plane of the surface. For filming extreme close-ups of

skin, leaves and other uneven surfaces, coherent light will show more detail. Landscapes have more

texture and depth when filmed in the morning or late afternoon-- especially at a 90 degree angle to

the light. Whenever you want the light to cast crisp, sharp shadows on a wall etc., coherent light is

definitely the way to go.

Coherent light is efficient because the energy travels with little or no obstruction. If you are trying to

light a background area with minimum wattage, a coherent light high and in-line with the camera may

produce the most foot-candles.

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BOLEX S-221 Technical Information Page 18