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Introduction
People go to theaters to witness spectacular plays, dances, symphonies,
and much more. Usually when the production starts, the house lights (the lights
on the audience) are turned off and the stage lights are turned on. Theater lights
are used to create effects on stage with colors, shapes, and enticing designs to
draw in an audience. After the idea of simply being able to see the stage, stage
lighting is used to highlight what is going on. An actor’s face must be evenly lit so
that the audience may read their expressions to fully understand what is
happening on stage. To be evenly lit, all of the lights on the actor’s face must be
very close in intensity levels. Intensity means how bright the light is, measured in
Lux, so the levels are how many Lux the light is set in. This can be done be
simply adjusting the levels with the technology used to control the lights.
However, depending on other factors affecting the light’s intensity, it may not be
truly even. These factors affect the audience’s ability to see the stage.
In this experiment, the researchers tested some possible factors for
varying light intensities to have information that allows lighting designers and
technicians to properly light a stage. These adjustments included angling the
lights differently, changing the distance at which the light was placed, and adding
or removing a colored gel. The angle was set by using a protractor and angling
the light downward to the desired angle from the horizontal. The distance was set
by using a meter stick to measure the desired distance between the stage light
and the light sensor. The gels were simply slid in front of the light’s lens when
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necessary. It was tested whether these adjustments had a significant effect on
the intensity of the light as projected on a surface. It was also determined which
combinations of these adjustments, and how much they were adjusted affected
the intensity the most.
To conduct the experiment, researchers used a Fresnel stage light angled
at different incident angles, at different distances, and different gel colors. The
light was then shined on a light sensor and the intensity in lux was recorded. A
D.O.E. was used to determine the interaction effects between the three factors.
Light designers and light technicians use intensity levels to evenly light
actors faces. The findings of similar experiments have helped them to make
adjustments that allow them to accomplish this more efficiently. Controlling light
intensity is a very important factor in theaters. Theaters are found all throughout
the world and this research can help improve upon the way stage lights are used
to impact light intensity.
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Review of Literature
Light intensity is a very important factor when dealing with stage lights.
Light intensity is how light spreads out over a certain area at a given distance.
Ultimately, it decides how bright the area will be. There are many factors related
to light intensity and many more that could affect it.
To start, readers must know about the electromagnetic spectrum. The
electromagnetic spectrum, or EM spectrum, is the range of frequencies of
different wavelengths. The researchers will focus on the visible light section of
the EM spectrum. As Gunderson stated in The Handy Physics Answer Book,
"visible light ranges from 4*1014 Hz to 7.9*1014 Hz." In other terms, the
wavelengths of the visible light spectrum ranges from "7.0 * 10 -7 meters to
approximately 4.0 * 10-7 meters" (Henderson, “Light Intensity”).The visible light
spectrum starts at red and goes up to violet. Refer to figure 1 below to see the
visible light spectrum. Each color has a certain wavelength that is created by
photons. The wavelengths are measured from crest to crest or trough to trough.
The red wavelengths are longer and the violet wavelengths are shorter. The
visible light spectrum is set up in order of low to high frequency. This means red
has the lowest frequency in the visible light spectrum while violet has the highest
frequency as stated in Irving Alder's Color In Your Life (15).
Figure 1. The Visible Light Spectrum (Henderson "Light Intensity")
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Light "waves carry energy" (Henderson "Light Intensity"). The shorter
wavelengths carry more photons so they have more energy. The more energy
there is, the higher the frequency, thus having a greater intensity. The colors
closer to violet on the visible light spectrum have shorter wavelengths so they
should have higher energy than the colors closer to red (McMillan). However, this
does not hold true when white light is changed to a different color using gel
colors. Colored gels only let through certain colors go through. For example: if we
have a laser pointer that shines green light, that green light will go through a
green colored gel, but it will not go through a red colored gel (Allain "Color
Example with Lasers"). When light hits an object some colors are reflected and
some colors are absorbed. The color that is reflected is the color that is seen.
The gels reflect the colors that the gel is, so if there was a blue gel, it would
reflect more of the blue and violet wavelengths so the light would be blue. The
pink gel would let in more of the reds, pinks, and yellows to make the light pink.
Pink gel lets in more photons than the blue gel so the pink gel would create a
light with higher intensity than the blue gel. White light on the other hand is when
all the wavelengths are reflected. With stage lights, there are no filters used to
create white light because it is not needed. Stage lights usually come with white
light bulbs. Since there is nothing blocking the path of the lights to only reflect
certain wavelengths, white light would have the highest intensity.
The next thing to understand is light intensity. Light intensity is perceived
as brightness. Intensity is the rate that light spreads over a certain surface at a
certain distance from a source. Henderson has stated and explained that
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distance will have an effect on the intensity (Henderson "Light Intensity"). As the
distance between the light source and object increases, the distance between the
light rays increases so it shines on a larger area. This means that the light is
more spread out and the light intensity of one spot is lower than it was at a closer
distance.
Light intensity is measured in lux, which is one lumen per square meter.
That means from one light source to one area and it measures the amount of
light at one square meter. A lumen is a measure of brightness, more specifically
it is the total amount of visible light that is present ("Energy 101: Lumens"). Area
does not matter for a lumen since a lumen is the same as the amount of light that
shines in a certain direction at a certain distance. There is no specific area that
lumens must be measured in, but when there is, that is measured in lux. One lux
is the same as 1000 lumens in an area of one square meter.
PASCO and Australia School of Innovation in Science, Technology, and
Mathematics (ASISTM) have done experiments relating to this topic. Both
experiments investigated the relationship between light intensity and the distance
from a light source. The experiments tested the level of light intensity at different
distances between the light source and the Lux meter or similar sensor
(PASCO). Their results showed that lux decreased as distance increased. The
PASCO lab was more complicated than the ASISTM lab, but both tested relevant
factors.
These experiments test distance like the researchers did in their
experiment. The researchers used the information found by ASISTM and PASCO
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to help with their hypothesis. They learned that the closest distances would
create the highest amount of lux. The researchers used the information found
about the wavelengths and how gel color affects it to help with creating the
hypothesis as well. This information backs up the claims the researchers made
and their hypothesis. One factor that was not found was how the angling of the
stage light affects intensity. The researchers tested a variable that had not been
tested before.
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Problem Statement
Problem:
To determine the effect of gel color, horizontal angle, and horizontal
distance of a Fresnel stage light on the light intensity at a fixed point that the light
is projected on.
Hypothesis:
The factors of horizontal angle, horizontal distance, and gel color
significantly affect the light intensity of the stage light.
Data Measured:
To measure the distance, the researchers used a meter stick and
measured in meters. The researchers used a protractor to measure the angle
below the horizontal that the light was projected at. They also used different color
gels to change the light color and amount of light able to pass through. They
measured the light intensity using a Lux meter that measures in lux.
The experiment was a three factor Design of Experiment (D.O.E.) The
experiment consisted of 44 trials, or 4 D.O.E.s of 11 trials each. The independent
variables were angle from the horizontal (15°, 30°, 45°) distance (1 meter, 2
meters, 3 meters), and gel color (none, pink #826, blue #859.) The dependent
variable was the light intensity, measured in Lux.
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Experimental Design
Materials:
TI-nspire
Meter Stick
Protractor
Fresnel Stage Light
Wooden Blocks (2x2x10 in)
Chair (60 cm)
Gel Frame (9.5 x 9.5 cm)
Stage Light Gel Pink #826
Stage Light Blue #859
Vernier LabQuest
Vernier Light Sensor (Lux)
Procedure:
1.
Using a TI-nspire calculator, randomize the trials within the 3-factor DOE.
2.
Set up one Fresnel stage light on a flat tabletop or other surface by
placing its base on the surface.
3.
Connect and set up the light sensor to the LabQuest.
a.
b.
c.
d.
e.
f.
g.
4.
Connect the light sensor to channel 1.
Click “Sensors.”
Click “Sensor Setup.”
Click “Channel 1.”
Click “Light.”
Click “Light 6000 lux.”
Click “ok.”
Place the LabQuest and light sensor on a flat surface 60 cm above the
ground. Keep the light sensor constant at a fixed point on the chair.
5.
Set light at the specific distance away from the light sensor for the first
randomized trial at 2 meters, 3 meters, or 4 meters, using the meter stick.
6.
Set up light at the angle for the trial using the protractor as in Figure 4. Tilt
the light down to the angle decided for the trial from the horizontal to
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achieve 15°, 30°, or 45°. Set the light up on wooden blocks as needed to
keep the hot spot on the light sensor (refer to Appendix B for hot spots).
7.
Slide the gel color for the trial into the gel frame. Slide the gel frame into
the gel frame holder in the front of the light.
8.
Turn all lights off. Zero the light sensor to simulate total darkness before
running the trial.
9.
Keep light sensor in darkness and plug in the light. Determine the light’s
center (refer to Appendix A).
10.
Record light intensity in lux as determined by the light sensor on the
LabQuest screen.
11.
Unplug the stage light.
12.
Repeat steps 4 through 11 for the remaining ten trials.
13.
Repeat the 3-factor DOE three more times to increase accuracy.
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Diagram:
Figure 2. Materials
Figure 2 shows the materials used in the experiment. More blocks were
used, but are not pictured. The chair was used to place the light sensor at a
constant 60 centimeters above ground and at the same point.
Figure 3. Diagram of the Set-Up
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Figure 3 is a diagram of the experimental set up. The distance is labeled
as “d” because the distance is a factor and changes according to different trials.
The chair in Figure 1 was used as the block shown in this figure to keep the light
sensor constant at one point and to keep it consistently at 60 cm above ground.
Figure 4. Measurement of the Incident angle
Figure 4 shows how the angle was calculated and from what horizontal it
was based off of. The 0° line of the protractor lines up with the horizontal line on
the gel frame holder.
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Data and Observations
Table 1
Factors and Values
Angle of Light
Standard
15
30
+
45
2
Distance of Light
Standard
3
+
4
Color of Light
Standard
+
white
pink
blue
Table 1 shows the variables for the experiment and the values that were
used. The work space was small so the researchers had to keep the angle and
distance within a reasonable range. The highest angle that could have been used
within the room was 45° and a chosen interval of 15° was used. Four meters was
the farthest distance away from the light sensor that the researchers could use
without going outside of the work space and still being able to keep the hotspot
on the light sensor. The blue color gel was used as the high because the color
blue is known to have the shortest wavelength which carries the most energy.
The gel colors were ordered from longest to shortest wavelengths.
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Table 2
Light Intensity Collected in Lux of each DOE
Runs
Order
Gel DOE #1 DOE #2 DOE #3
Angle Distance
Color
1
482
540
544
2
77
54
81
+
+
+
3
2156
2145
2177
4
458
450
387
+
+
5
155
162
153
+
+
6
480
548
545
7
114
113
103
+
+
8
1257
1267
1224
+
9
580
586
559
+
10
376
377
382
+
11
498
544
539
-
DOE #4
541
67
2155
400
137
522
108
1250
555
400
511
Table 2 shows the order of the runs, the runs, and the results of each
DOE of the researchers’ experiment. The results show light intensity measured in
lux.
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Table3
Averages of Testing Results
Runs
First Second
Gel
DOE
DOE
Angle Distance
Color
+
+
+
77
54
2156
2145
+
+
458
450
+
+
155
162
+
+
114
113
+
1257
1267
+
580
586
+
376
377
Third
DOE
Fourth
DOE
81
2177
387
153
103
1224
559
382
Average Light
Intensity (lux)
67
2155
400
137
108
1250
555
400
Grand
Average:
69.75
2158.25
423.75
151.75
109.5
1249.5
570
383.75
639.53125
Table 3 shows the averages of the light intensities of all of the runs,
except the standards, in all of the Design of Experiments. The grand average is
also shown.
Table 4
First DOE Observations
Order
Observations
Number
1
The trial was run by Researcher 1 only.
2
No significant observations.
3
The trial was run by Researcher 1 only.
4
No significant observations.
5
No significant observations.
6
The trial was run by Researcher 1 only.
7
The trial was run by Researcher 1 only.
8
No significant observations.
9
The trial was run by Researcher 1 only.
10
The trial was run by Researcher 1 only.
11
The trial was run by Researcher 1 only.
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Table 5
Second DOE Observations
Order
Observations
Number
1
The trial was run by Researcher 1 only.
2
No significant observations.
3
The trial was run by Researcher 1 only.
4
No significant observations.
5
No significant observations.
6
The trial was run by Researcher 1 only.
7
The trial was run by Researcher 1 only.
8
No significant observations.
9
The trial was run by Researcher 1 only.
10
The trial was run by Researcher 1 only.
11
The trial was run by Researcher 1 only.
Table 6
Third DOE Observations
Order
Observations
Number
1
The trial was run by Researcher 1 only.
2
No significant observations.
3
No significant observations.
4
No significant observations.
5
No significant observations.
6
No significant observations.
7
No significant observations.
8
No significant observations.
9
The trial was run by Researcher 1 only.
10
No significant observations.
11
The trial was run by Researcher 1 only.
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Table 7
Fourth DOE Observations
Order
Observations
Number
1
No significant observations.
2
No significant observations.
3
No significant observations.
4
No significant observations.
5
No significant observations.
6
No significant observations.
7
No significant observations.
8
No significant observations.
9
No significant observations.
10
No significant observations.
11
No significant observations.
Tables 4, 5, 6, and 7 show the observations for the four DOEs. Orders 1,
3, 6, 7, 9, 10, and 11 of Tables 4 and 5 had only one researcher running the
trials. Those trials were more difficult to perform because the light sensor was not
zeroed out right before the light was turned on by another researcher which may
have affected the results. Also Researcher 1 is less experienced with stage lights
so there may be some error in the results. In Table 6, orders 1, 9, and 11 were
performed by one researcher and the trials were harder to conduct. Both
researchers were present for each trial. Trials ran smoothly.
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Data Analysis and Interpretation
The researchers used a three-factor Design of Experiment (DOE) in this
experiment. It tests how three predictor variables and their interactions affect a
response variable. The researchers tested how the incident angle, horizontal
distance, and gel color of a Fresnel stage light affected light intensity (measured
in lux). Four DOE's were conducted.
The data was collected by finding the hotspot of the Fresnel stage light
and aiming it at the light sensor at the specified angle and distance with the
appropriate gel color or lack thereof. The data collected was reliable because
there were standard trials. These trials showed what lux was achieved when
standard values of angle, distance, and gel color are used. The standards show
whether the high and low values had any effect on the light intensity.
The trials from all four DOE's were randomized with a TI-nspire calculator
and performed in that random order to make sure ensure good data and reduce
confounding. One characteristic lacking randomization was that Researcher One
did many of the beginning trials, while Researcher Two did the later trials.
Researcher Two is more familiar with finding hotspots and Researcher One is
not. There may have been some difference in data collection due to different
perceptions of hotspots.
Four DOE's were completed in the experiment. Each trial was repeated
four times. The repetition shows whether or not the variables do have an effect
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on light intensity. It also decreases the chance of false data. The Law of Large
Numbers states that more data results on less varied results.
In each DOE, there were 11 trials. The random number integer function on
the TI-nspire helped to randomize the trials. The trials were numbered then
conducted in this random order, but the standard trials were always the first,
middle, and last trials to be done. Table 1 shows the factors and values used for
the experiment. The standard values were 30° at the incident angle, 2 meters
away from the light sensor, and the use of the pink gel.
After all the trials were conducted, the twelve standards were analyzed
first. As seen in Table 8 below, the light intensity of the standards are fairly
consistent. The standards were also graphed together as seen in Figure 5.
Figure 5 further proves that the experiment was controlled and had little
variability. The first three standards were the only ones that seemed significantly
different. This could be due to the fact that Researcher One was alone that day
and ran the trials by herself. Researcher One is not as well acquainted with
finding hotspots so that may have affected the standard values. This means that
the experiment was not conducted completely correctly.
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Table 8
Twelve Standards
12 Standards
482 480 498 540 548 544 544 545 539 541 522 511
Light Intensity (lux)
Twelve Standard Runs
600
580
560
540
520
500
480
460
440
420
400
0
1
2
3
4
5
6
7
Trials
Figure 5. Twelve Standard Runs
19
8
9
10
11
12
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FACTOR: Angle
Table 9
Angle Effect
Angle
(-) 15°
(+) 45°
Effect of Angle
69.75
109.50
423.75
570.00
151.75
383.75
1249.50
Grand
Average =
805.38
Grand
Average =
473.69
Light Intensity (lux)
2500
2158.30
2000
1500
1000
805.375
500
473.6875
0
-1
1
Angle
Figure 6. Effect of Incident Angle
The effect of angle is -331.6875 (the change from low to high). On
average, as angle increases, the light intensity decreases by 331.6875 lux.
Figure 6 shows the effect of incident angle on light intensity. Table 9 shows the
eight averages for the low and high values of angle. It also shows the total
average effect on the low and high values.
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FACTOR: Distance
2158.3
69.75
151.75
423.75
1249.5
109.5
383.75
570
Grand
Average =
985.81
Effect of Distance
2500
Light Intensity (lux)
Table10
Distance Effect
Distance
(-) 2
(+) 4 meters
meters
2000
1500
985.8125
1000
500
293.25
0
Grand
Average =
293.25
-1
1
Distance
Figure 7. Effect of Horizontal Distance
The effect of distance is -692.5625 (the change from low to high). On
average, as distance increases, the light intensity decreases by 692.5625 lux.
Figure 7 shows the effect of horizontal distance on light intensity. Table 10 shows
the eight averages for the high and low values of distance and the total average
effect on the high and low values.
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FACTOR: Gel Color
Table 11
Gel Color Effect
Gel Color
(-) white
(+) blue
69.75
423.75
151.75
1249.5
109.5
570
383.75
Grand
Average =
1100.4
Grand
Average =
178.69
Light Intensity (lux)
2158.3
Effect of Gel Color
2500
2000
1500
1100.375
1000
500
178.6875
0
-1
1
Gel Color
Figure 8. Effect of Gel Color
Effect of gel color is -921.6875 (the change from low to high). On average,
as gel color changes from low to high, light intensity decreases by 921.6875 lux.
Figure 8 shows the effect of gel color on the light intensity. Table 11 shows the
eight averages for the high and low values of gel color and the total average
effect on those values.
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TWO FACTOR INTERACTIONS: Interaction of Angle and Distance
Table 12
Angle vs. Distance
Angle
(+) 45°
(-) 15°
(+) 3
meters
246.75
339.75
(-) 1
meter
700.625
1271
Distance
Figure 9. Interaction of Angle and
Distance
The slope of the line segment of high factor of distance (+) minus the
slope of the line segment of low factor of distance (-) gives the Effect (Angle vs.
Distance) = (-46.5) - (-285.1875) = 238.6875. Table 12 shows the values used for
the interaction effect. Figure 9 shows the interaction effect between angle and
distance. The slopes are not parallel, which means there is a possibility of an
interaction. When distance was low light intensity was around 985 lux, but when
angle was taken into effect the lux was at 247 to 340 lux. Also, when the distance
was high, the light intensity was around 293 lux. With the addition of angle, the
light intensity was between 700 lux and 1271 lux. The light intensity values for
the interaction between angle and distance were not what was expected. This
shows that there is a possible interaction.
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TWO FACTOR INTERACTIONS: Interaction of Angle and Gel Color
Table 13
Angle vs. Gel Color
Angle
(+) 15°
Gel
Color
(-) 45°
(+) Blue
Gel
110.75 246.625
(-) No
Gel/White
Light
836.625 1364.13
Figure 10. Interaction of Angle and Gel Color
The slope of the line segment of high factor of gel color (+) minus the
slope of the line segment of the low factor of gel color (-) = (-67.9375) - (263.7525) = 195.815. Table 13 shows the values used for the interaction effect.
Figure 10 shows the interaction effect between angle and gel color. The slopes
are not parallel so there is a possibility of an interaction between the two factors.
When gel color was low light intensity was around 1100 lux, but when angle was
taken into effect the lux was between 110 to 250 lux. Also, when the gel color
was high, the light intensity was around 180 lux. With the addition of angle, the
light intensity was between 840 lux and 1360 lux. The light intensity values for
the interaction between angle and gel color were not what was expected. This
shows that there is a possible interaction.
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TWO FACTOR INTERACTIONS: Interaction of Distance and Gel Color
Table14
Distance vs. Gel Color
Distance
(+) Blue
Gel
Gel
Color
(-) No
Gel/White
Light
(+) 4 m
(-) 2 m
89.625
267.75
496.875 1703.88
Figure 11. Interaction Effect of Distance and
Gel Color
The slope of the line segment of high factor of gel color (+) minus the
slope of the line segment of the low factor of gel color (-) = (-89.0625) - (603.5025) = 514.44. Table 14 shows the values used for the interaction effect.
Figure 11 shows the interaction effect between distance and gel color. The
slopes differ, meaning there is a possibility of an interaction. When gel color was
low light intensity was around 1100 lux, but when distance was taken into effect
the lux was between 90 and 270 lux. Also, when the gel color was high, the light
intensity was around 180 lux. With the addition of distance, the light intensity was
between 500 lux and 1700 lux. The light intensity values for the interaction
between gel color and distance were not what was expected. This shows that
there is a possible interaction.
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Overall effects of single factors:
Effect of Incident angle = -331.6875
Effect of Horizontal Distance = -692.5625
Effect of Gel Color = -921.6875
Interactions Between Factors:
Effect of Angle and Distance = 238.6875
Effect of Angle and Gel Color =195.815
Effect of Distance and Gel Color =514.44
Table 3 shows the grand average of all the trials, which is 639.53125 lux.
This grand average was used in the prediction equation found in Figure 12
below. In the equation variables are used to denote the predictor variables of a
DOE. For the sake of coherence, the variables in the equation will denote the
predictor variables of this experiment. The symbol A stands for angle, B stands
for distance, and C stands for gel color. This equation represents the grand
average added to the individual effects and the interaction effects of the predictor
variables each divided by two.
EffectofA
EffectofB
EffectofC
InetractionofA & B
* A
*B
*C 
* AB 
2
2
2
2
InetractionofA & C
InetractionofB & C
* AC 
* BC
2
2
Y  GrandAverage 
Figure 12. General Prediction Equation
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The prediction equation was then used in the researchers' experiment.
The researchers plugged in their values to create the equation found in Figure 13
below. One can insert high, low, or any other values of angle, distance, and gel
color to predict the light intensity present in lux.
Y  639.53125 
 331.6875
 692.5625
 921.6875 238.6875
195.815
514.44
* A
*B 

* AB 
* AC 
* BC  Noise
2
2
2
2
2
2
Figure 13. Prediction Equation of the Experiment
The next step for the researchers was to create a dot plot of effects. This
would help them decide which factors were significant. Figure 14 shows the dot
plot of effects below.
Figure 14. Dot Plot of Effects
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Table 15
Test of Significance
Effect
Value
Divided By
The Range
of Standards
Answer
Effect of Angle
-331.6875
548-480=68
-4.878
4.878 Yes
Effect of Distance
-692.5625
68
-10.18
10.18 Yes
Effect of Gel color
-921.6875
68
-13.55
13.55 Yes
Interaction of Angle &
Distance
238.6875
68
3.5101
3.5101 Yes
Interaction of Angle &
Gel Color
195.815
68
2.8796
2.8796 Yes
Interaction of Distance
and Gel Color
514.44
68
7.5653
7.5653 Yes
Effect or Interaction
Absolute
Value of
the Effect
Vital?
The researchers decided that all of the factors are significant because
they all seemed vital. They came to this conclusion by performing a test of
significance shown in Table 15. In the test of significance, the range of the
standards (maximum standard minus minimum standard) divides the effect. If
the absolute value of this quotient is greater than or equal to 2, it is considered
significant. In this experiment, all the values were found to be significant since
their answers were greater than two.
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Since the researchers deemed everything as significant, all values were used in
the parsimonious equation. Figure 15 shows the parsimonious equation below.
The symbol A stands for angle, B stands for distance, and C stands for gel color.
Y  639.53125 
 331.6875
 692.5625
 921.6875 238.6875
195.815
514.44
* A
*B 

* AB 
* AC 
* BC " Noise"
2
2
2
2
2
2
Figure 15. Parsimonious Equation
According to the Design of Experiment the effect of angle, distance, and
gel color all had negative effects on light intensity. All the interactions had a
positive effect on the light intensity. The DOE deemed each factor and interaction
as significant. This means that the angle of the light, the distance away from the
light sensor (or a fixed point), and the gel color (or change in color of the light)
had an effect on the light intensity at that fixed point.
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Conclusion
This experiment was conducted to test whether or not the incident angle,
horizontal distance, and gel color (or lack thereof) of Fresnel stage light affected
light intensity. The researchers accepted their hypothesis that all the factors
would have an effect on light intensity. Some special materials used in this
experiment to come to this conclusion were the Vernier LabQuest, a Vernier light
sensor, pink #826 gel, and blue #859 gel. The Fresnel stage light was placed at a
certain low, high, or standard distance away from the light sensor and angled at a
certain low, high, or standard incident angle. According to the trial, there was a
pink, blue, or no gel attached to the stage light. Table 16 below shows the values
used for each factor.
Table 16
Factors with their Values
Angle of Light (°)
Distance of Light (m)
-
Standard
15
30
+
-
45 2
Color of Light
Standard
+
-
Standard
+
3
4
white
pink
blue
It was believed that the incident angle, the horizontal distance, and the gel
color would significantly affect the light intensity of the stage light. A three factor
Design of Experiment was used to test each effect and their interactions. That
means that every factor that was tested was significant which confirms the
researchers’ hypothesis. The researchers confirmed their hypothesis that the
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incident angle, the horizontal distance, and gel color were all significant in
affecting the light intensity of the stage light.
The first of the effects was incident angle. The researchers did not find
any previously recorded data which indicates that angle to be a major influence
on light intensity in this setting. They did however find that when the sun is at a
larger angle from the surface of the earth, the earth is hotter and receives more
of the sun's rays. When it is at lower angles to the earth's surface, that area
receives less sunlight. The angle of the sun to the earth's surface has an impact
on the amount of sunlight the area receives. The researchers believed that the
same idea applied to the stage light. When the stage light was at a high angle the
light intensity was around 800 lux. When it was at the low angle the light intensity
was less; it was at 470 lux. The change in lux told the researchers that angle
might have had an effect on light intensity.
The second factor was horizontal distance. In the process of research, the
researchers found that distance did have an effect on light intensity. "Intensity is
used to describe the rate at which light spreads over a surface of a given area
some distance from a source" (Henderson). This quote, written by a chemical
engineer, shows that distance is directly related to light intensity. Light carries
photons in straight lines in all directions. The rays get farther apart as the
distance increases. Since the rays grow farther apart from one another, the light
spreads out over a larger surface. Because of this, the light is not focused on one
object. This shows that as the light source gets farther and farther from the light
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sensor, the sensor picks up scattered light rays and the intensity is therefore
lower. When the light source is closer, the rays are directed to one object and are
not so spread out, so the source picks up more light waves and the intensity is
higher.
The final factor was gel color. Light waves carry energy and shorter
wavelengths have more energy. The colors that are closer to violet have shorter
wavelengths so they would have more energy. However, that is not the case with
gel colors. The gels are colored so they only allow certain types of light through
the gel. The blue gel would only let in blue and violet and it wavelengths so there
would be fewer photons going through it. Because of that, the light intensity
should have been low and it was. The low value (which was white) with no gel
color, just white light, would have nothing blocking any photons. This would mean
that it would have the highest light intensity. The researchers used blue as the
high value because it had the shortest wavelength, but it had the lowest intensity.
A design flaw was that the researchers did not have access to
many platforms or blocks to place the stage light on. There were not enough
blocks to hold up the stage light at the highest angle so the hotspot was on the
light sensor. The researchers had to improvise and hold the light sensor up to
keep it at the correct angle with the hotspot on the sensor. Researcher 2 did this
each time so it was one person constantly doing the task. However, the stage
light is not easy to hold up above head and calculate the hotspot at the same
time. This meant that the hotspot was not always perfectly centered when the
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measurement was taken. To enhance this experiment, the researchers could
have been more prepared.
For further research, the experiment can be conducted on an actual stage
to see if there is a large-scale affect with the factors. Future researchers could
also test larger angles. Different types of gels can also be tested.
Light intensity in theater is how bright the light is as it appears on stage.
Light intensity is a major factor in theaters across the world. Lighting designers
and lighting technicians prepare for and control a theater's lights during a show or
production. They must make sure that the actors' faces are completely
illuminated by the light at all angles to fully understand the actors' facial
expressions. The emotion will not be felt if the facial expressions cannot be seen
well. Therefore, knowledge on what factors significantly affect light intensity
would be necessary in the theatrical world. This knowledge allows lighting
designers and technicians to control and manipulate each individual light’s
intensity in order to achieve their common goal in properly lighting the stage in
order to please the audience.
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Acknowledgements
The researchers would like to thank James Higgenbottom, the Auditorium
Director at Warren Woods Community Theater, for lending the researchers the
Fresnel stage light and its accessories. They would also like thank Mr. McMillan
for correcting the scientific elements of the research paper. The researchers
would like to express their thanks to Mrs. Cybulski for correcting the grammar
and structural elements of the research paper. Finally, the researchers would like
to thank Lori Dickerhoff, Head Lighting Technician and Designer at Warren
Woods Community Theater, for being a consultant on theater lighting and
reviewing the research paper. They express great thanks to all who have helped
with and during the time of research.
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Appendix A
How to Identify the Hotspot
To find the hotspot, the stage light must be turned on. It should be shined on the
ground. Observe the brightest spot on the ground which is usually the center.
The stage light should be moved to its position on top of the blocks. The hotspot
should then be on the light sensor. Usually the high angle, high distance, and
high gel color trials have the stage light 2 meters and 30 centimeters above the
ground with the hotspot on the light sensor. The low angle, low distance, and low
gel color trials usually had the stage light 1 meter 7 centimeters above the
ground. The high angle, high distance, and low gel color trials had the stage light
2 meters and 24 centimeters above the ground. The high angle, low distance,
and high gel color trials had the stage light 1 meter and 84 centimeters above the
ground. The low angle, high distance, and high gel color trials had the stage light
approximately 1 meter and 58 centimeters above the ground. The high angle, low
distance, and low gel color trials had the stage light approximately 2 meters
above the ground. The low angle, high distance, and low gel color trials had the
stage light 1 meter 8 centimeters above the ground. The low angle, low distance,
and high gel color had the stage light about 1 meter 7 centimeters above the
ground. The standard trials had the stage light around 1 meter and 59
centimeters above the ground.
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