Dimming & Distribution

Dimming & Distribution
o
DIMMERS
1. Sabbatini (1574-1654) envisioned a mechanical candle douser
2. In the 19 th Century, gas light intensity was controlled by a gas table
3. With the advent of electric light, dimming was accomplished using
Variable Resistance devices, first was the Saltwater Dimmer

Dimming & Distribution
o
DIMMERS
1. Sabbatini (1574-1654) envisioned a mechanical candle douser
2. In the 19 th Century, gas light intensity was controlled by a gas table
3. With the advent of electric light, dimming was accomplished using
Variable Resistance devices, first was the Saltwater Dimmer
• Current was controlled by how much
of a metal plate was submerged in the
salt water
• It was highly dangerous, the current
could produce toxic chlorine gas or
flammable hydrogen and oxygen
• The water level and salt
concentration had to be constantly
maintained, colloquially known as
“piss pots“

Dimming & Distribution
o
DIMMERS
4. Resistance Dimmers replaced salt water dimmers
• Consisted of a round plate, the resistance plate was made of
lengths of copper wire
• The electrical resistance converted excess power into heat

Dimming & Distribution
o
DIMMERS
4. Resistance Dimmer
• Consisted of a round plate, the resistance plate was made of
lengths of copper wire
• The electrical resistance converted excess power into heat
• The dimmers not only had a maximum load (current) but also a
minimum load to accomplish a complete fade out
• In order to make these minimum loads without adding extras
lights on stage resistance, dimmers were loaded with Ghost
Loads which were additional lighting equipment placed
offstage or behind the theatre

Dimming & Distribution
o
DIMMERS
4. Resistance Dimmer
• Resistance was varied by changing the amount of wire the
current had to pass through
More Resistance
Dimmer
Less Resistance
Brighter

Dimming & Distribution
o
DIMMERS
4. Resistance Dimmer
• The electrode was moved by a mechanical lever, groups of
dimmers and levers were mounted in boards
• A master lever allowed control of all of the dimmers in a board
• Required 6-8 electricians to run one light cue
• This method was used well into the 1970’s

Dimming & Distribution
o
DIMMERS
5. Autotransformer Dimmer
• Consists of copper wire wound around a doughnut shaped
iron core to create an inner primary coil and an outer
secondary coil
• Like a standard two coil transformer, the ratio between the
windings determines the output voltage

Dimming & Distribution
o
DIMMERS
5. Autotransformer Dimmer
• A brush makes contact with the secondary coil allowing the
number of winding (and the ratio) to be varied
• Lowering the ratio lowers the output voltage and dims the load
• Unlike Resistance Dimmers, load did not need to be matched

Dimming & Distribution
o
DIMMERS
5. Autotransformer Dimmer
• Dimmers were often mounted in package boards consisting of
six dimmers, circuit breakers and patching plugs, a larger
autotransformer would act as a “master”
• Brush mechanism could be attached to a motor for control

Dimming & Distribution
o
DIMMERS
6. Silicon Controlled Rectifier (SCR) Dimmer
• Developed by GE in 1956
• A solid state device (doesn’t contain vacuum tubes or relays)
• Controls the flow of current, switches on and off 120 times/sec
• Dims the light by use of the Gating Principle

Dimming & Distribution
o
DIMMERS
6. Silicon Controlled Rectifier (SCR) Dimmer
• Dims the light by use of the Gating Principle
The human eye perceives anything greater than 24 frames
per second as continuous
The SCR Gate opens for a portion of each cycle
If the Gate is open for half of each cycle, then the light is
“on” for ½ second out of every second and is perceived as
being at 50% intensity

Dimming & Distribution
o
DIMMERS
6. Silicon Controlled Rectifier (SCR) Dimmer
• Parts of a SCR dimmer
Choke : donut shaped coil. houses the SCR, reduces hum
and smoothes out power spikes
Magnetic Circuit Breakers : protect SCR from excessive load
This ETC Sensor Dimmer houses two separate dimmers
• This allows for electronic control of dimming

Dimming & Distribution
o
ELECTRICAL DISTRIBUTION
Types of theatrical systems
1. Dimmer-Per-Circuit System (Studio Theatre)
FIXTURE (load) – CIRCUIT – DIMMER – CONTROLLER (lightboard)
2. Distributed Dimming System (Player’s Theatre)
FIXTURE – DIMMER – CONTROLLER (dimmer is located at the fixture)
3. Patch System (Player’s Theatre, University Theatre)
FIXTURE – CIRCUIT – PATCH PANEL – DIMMER – CONTROLLER

Dimming & Distribution
o
ELECTRICAL DISTRIBUTION
Types of theatrical systems
3. Patch System (Player’s Theatre, University Theatre)
FIXTURE – CIRCUIT – PATCH PANEL – DIMMER – CONTROLLER
• Raceway – distributes circuits across a batten or pipe

Dimming & Distribution
o
ELECTRICAL DISTRIBUTION
Types of theatrical systems
3. Patch System (Player’s Theatre, University Theatre)
FIXTURE – CIRCUIT – PATCH PANEL – DIMMER – CONTROLLER
• Slider Patch Panel – connects circuits to dimmers
• Telephone Patch Panel

Color Theory
o
White light is made up of all visible colors

Color Theory
o
o
White light is made up of all visible colors
The visible spectrum is a narrow band of electromagnetic radiation

Color Theory
o
Perceiving Color
1. Retina is comprised of rods and cones
2. Rods are photoreceptive cells concentrated on outer edges of the
retina, function in low light, responsible for night and peripheral vision
3. Cones are photo cells that only function in bright light, fast response
time allows finer detail to be seen, also responsible for color vision

Color Theory
o
Perceiving Color
1. Retina is comprised of rods and cones
2. Rods are photoreceptive cells concentrated on outer edges of the
retina, function in low light, responsible for night and peripheral vision
3. Cones are photo cells that only function in bright light, fast response
time allows finer detail to be seen, also responsible for color vision
• There are three different types of Cones that detect red, green
and blue wavelengths
4. Rods and Cones send signals to the brain through the optic nerve

Color Theory
o
Terminology
1. Hue : the different colors, Primary Hues (Red, Green, Blue) and
Secondary Hues (Cyan, Magenta, Yellow or Amber)

Color Theory
o
Terminology
1. Hue : the different colors, Primary Hues (Red, Green, Blue) and
Secondary Hues (Cyan, Magenta, Yellow or Amber)
2. Saturation : or chroma, the amount of pure spectral hue in a color
3. Value : the relative lightness or darkness of a hue (paint)

Color Theory
o
Terminology
1. Hue : the different colors, Primary Hues (Red, Green, Blue) and
Secondary Hues (Cyan, Magenta, Yellow or Amber)
2. Saturation : or chroma, the amount of pure spectral hue in a color
3. Value : the relative lightness or darkness of a hue (paint)
• Tint is a high value (more white) color
• Shade is a low value (more black) color
• Tone is a mid value color

Color Theory
o
Color Interaction
1. Color Triangle
• Primary Colors are located at the corners
• Secondary Colors result from the mixing of two primaries
• Complementary Colors are opposites on the triangle

Color Theory
o
Color Interaction
2. Additive Color Mixing
• Light projected onto a white surface or in the air mixes
• The three Primaries or the three Secondaries mix to white
• Two Complementary colors mix to white

Color Theory
o
Color Interaction
2. Additive Color Mixing (Primaries)

Color Theory
o
Color Interaction
2. Additive Color Mixing (Complements)

Color Theory
o
Color Interaction
3. Color Filtering (Subtractive Mixing)
• Placing a gel in front of a light filters or prevents selected colors
from passing through

Color Theory
o
Color Interaction
3. Color Filtering (Subtractive Mixing)
• Placing a gel in front of a light filters or prevents selected colors
from passing through

Color Theory
o
Color Interaction
3. Color Filtering (Subtractive Mixing)
• Magenta gel (R+B) and Cyan gel (G+B) results in blue light

Color Theory
o
Color Interaction
3. Color Filtering (Subtractive Mixing)
• Yellow gel (G+R) and Cyan gel (G+B) results in green light

Color Theory
o
Color Interaction
3. Color Filtering (Subtractive Mixing)
• Yellow gel (G+R) and Magenta gel (B+R) results in red light

Color Theory
o
Color Interaction
3. Color Filtering (Subtractive Mixing)
• Any two Primaries or all secondaries result in no light transmission

Color Theory
o
Color Interaction
4. Color Reflection
• The color of an object is determined by the color it reflects

Color Theory
o
Color Interaction
4. Color Reflection
• The color of an object is determined by the color it reflects
• An object’s color can be modified by color the color of light

Color Theory
o
Color Interaction
4. Color Reflection
• The color of an object is determined by the color it reflects
• An object’s color can be modified by color the color of light
• A primary red costume under primary blue light appears black
because pure blue light had no red in it

Color Theory
o
Color and Lamps
1. Color Temperature
• “White” light from different types of lamps are not the same
• Color temp can affect the color produced by a gel because
wavelengths are present in different quantities

Color Theory
o
Color and Lamps
2. Color Correction
• Filters that adjust the color temperature of a lamp to match
another type of lamp
• CTO (color temperature orange) corrects high color temp (blue)
to lower color temp (orange or amber), Arc to Tungsten
• CTB (color temperature blue) corrects low color temp to higher
color temp, Tungsten to Arc
• Minus-Green filters out green light, useful for correcting the
green tint of fluorescent lights
• Plus-Green provides a green cast, Tungsten to Fluorescent
3. Amber Drift
• As an incandescent lamp is dimmed it’s color temperature
lowers radiating a warmer light, shifting towards amber
• This affects gel color in lights running at low intensity
• Not a problem with arc or discharge sources

Color Theory
o
Color Media
1. Plastic Media – commonly called gels short for original gelatin media
• Made of polyester or polycarbonate impregnated with dye
• Developed for use with higher temperature quartz lamps
• Standard nomenclature : R or X = Roscolux, L = Lee, G = GAM

Color Theory
o
Color Media
2. Colored Glass
• Colored glass Roundels are found in striplights and other
instruments that remain on for long periods
• Resists heat and color never fades

Color Theory
o
Color Media
3. Dichroic Glass
• Rather than absorbing unwanted color, dichroics reflect color
back to the source
• An amber dichroic reflects complement blue back to the source
• Resists heat, creates more saturated colors than gels
• Used extensively in moving fixtures