Mirrors II

by Terry Cobb, University of Maryland Baltimore County

In my last article, I inadvertently gave the impression to some
that I was the lighting designer for all the productions from which
the examples were drawn. In one example, The Glass Menagerie,
although the idea for the use of mirror was mine, the lighting
designer was Billie Simms, a student at the time. My apologies for
the oversight.

The proposed use of mirror at the end of the last article as a
footlight-like device was indeed utilized successfully in the UMBC
production of Marat/Sade in May of this year. The flat mirror idea
did not work because the coverage area was not adequate for the
application. The mirror width had to be less than a foot. So simple
geometry would show that with a throw of twelve feet from the
lighting source to the mirror and an additional six to ten feet of
travel before striking the actors, the maximum width of the
reflected beam was going to be less than two feet. Knowing this, I
went back to the curved mirror idea. In the previous applications,
The curved mirror was constructed using curved ribs running across
the narrow dimension of the mirror, i.e., up and down stage. The
mirrorplex was bent against this ribs to create the curve.

The result of this method was that the mirror curved nicely at the
ribs but tended to flatten between them, creating a pronounced
distortion. Noting this, for this application I changed the design
so that a single well-braced rib ran along the long axis of the
curve. This produced a more nearly uniform curved surface so that
the light reflected off the mirror was not nearly so distorted as
the previous method. It was not perfect but for this production
that imperfection was applicable to the scenes in which the
footlight effect was used. I would suggest that producing a good
quality optical curve would require continuous bonding of the
mirrorplex to a uniform continuous curved surface, not an easy
task.

The effect of the reflected light from the mirror using the single
long rib method of construction was fairly good for the nightmarish
scenes in which it was used. I was able to cover an area extending
from approximately six feet off the floor to approximately six feet
high at four to five feet distance from the mirror. Farther
upstage, the coverage was floor to ceiling. This could be varied
somewhat by the placement of the lighting instruments in relation
to the mirror. Moving the lighting instrument upstage in relation
to the mirror would increase the top coverage but reduce the bottom
coverage. A limit exists in this method of adjustment in that at
some point the actor starts to interfere with the travel of the
light from the light fixture to the mirror. Changing the amount of
curve would also change the coverage.

By using 750 watt lekos at our twelve foot throw, adequate
illumination could be achieved to cover actors on the asylum bars
25 feet upstage and eight to ten feet off the floor. Each leko was
covering six to eight feet of mirror. I did find that the lekos
needed to be very finely aligned and focused to produce a
reasonable clarity of illumination. The brightness of the light was
fairly even along a vertical axis but broke up into brighter and
dimmer bands as one moved horizontally across the stage. This
effect was consistent and the reflected light did indeed fall into
a rectangle. This was not the case in the curved rib construction.
In that case, crazed patterns were projected at random areas of the
set until the diffusion materials were placed on the mirror.

In conclusion, this use of mirror to substitute for a footlight
does work for some applications. Certainly it does not produce the
brightness of direct lighting by actual strip type units. It can be
accomplished in less space. It produces better coverage that "a
bunch of lights under the front row" ever would. In this
application, there was an ethereal quality, particularly when
combined with the blue-green color used, which was perfect for
those scenes. A particularly good point for this production was
that there were no hot surfaces and no sharp edges for the patients
to either burn themselves on or get their costumes caught on. As
the lekos must be shuttered down to a narrow strip, the efficiency
of the fixture is relatively low. This was not a "bright" effect in
relation to stage lighting to which we are accustomed.