Illumination: Exploring Dark Adaptation and Opponent Color Theory

This lab report explores the phenomena of dark adaptation and opponent color theory, providing insights into the human visual system. The first experiment investigates dark adaptation, detailing the procedure of moving from a bright environment to a dark room and observing the time it takes to perceive objects of varying colors. The results highlight the role of pupil dilation, rhodopsin reactivation, and the activation of rods and cones in the retina. The discussion explains the order in which objects become visible, linking it to light reflectance and the photoreceptors involved. The second experiment examines the opponent color theory, where a red object is viewed for a period, followed by observations of an afterimage. The discussion explains how the cones, arranged in opposing pairs, become fatigued, leading to the perception of the opposing color. The report includes the experimental procedures, results, and discussions, along with relevant references.

Running HEAD: ILLUMINATION 1
Illumination
Name
Institution
Date

ILLUMINATION 2
Activity 1
Investigation of the dark adaptation phenomena.
Introduction
Dark adaptation phenomena is the gradual ability to detect the contents of a dark room after
suddenly getting into the dark room from an area with a high light intensity (Reuter, 2011).
Procedure
 A set of 5 objects of color ranging from white to black were prepared
 A space in a dark room with minimal light was prepared and the objects arranged as
shown below.
 I spent five minutes in the sun, an area with high light intensity.
 A timer was set to recur every two minutes
 I then got into the dark room and immediately started the timer and focused on the space
where the objects were arranged.
 After I was able to see the darkest object, I stopped the timer.
Results
The white object was clearly seen a minute after getting into the room, the grey objects were
clearly seen after 10 min while the black object was seen after 22 minutes.

ILLUMINATION 3
Discussion
After spending time in the sun.
After spending time in the sun, the following happened to the eye.
 The pupil, an aperture that lets light into the eye, contracts to limit the amount of light
getting into the retina.
 The rhodopsin, the light sensitive chemical in the cones, cells in the retina that cause
color vision, are photobleached hence making them inactive due to the high light
intensity.
After getting into the dark room
 The pupil dilates in order to let in more light due to light inadequacy in the room. This
happens in matter of seconds.
 The rhodopsin reactivates and regenerate in order to become light sensitive. This takes up
to 10 minutes.
 The rhodopsin of the rod cells in the retina, responsible for the black and white vision and
that enable vision in low light intensity are activated. This takes longer from 20min to
several hours.
Discussion of the observation
 It was possible to see the white object within a minute because the iris was able to dilate
and allow some light into the retina
 The grey objects were visible within 10 minutes because the rhodopsin in the cons were
activated and hence adapted to the partial darkness.

ILLUMINATION 4
 After the activation of the rods after 20 minutes, it was possible to see the dark object.
Discussion of the order at which the images were seen.
White objects reflect more light than black objects. The reflectance level decreases with decrease
in brightness. Detection of objects is possible due to the light they reflect and get into the eyes of
the viewer. This caused the vision time of the objects range from 1 minute to 22 minutes
depending on the photoreceptors available in the retina for image formation as discussed above.
Below is the dark adaptation curve
Fig 1. Dark adaptation curve. Retrieved from https://wtamu.edu/~cbaird/sq/2013/08/09/how-long-
does-it-take-our-eyes-to-fully-adapt-to-darkness/

ILLUMINATION 5
Activity 2
Opponent color theory investigation
Introduction
Opponent color theory explains the human eye are only able to detect one of the opposing colors
at a time. These opposing colors are blue and yellow, red and green and black and white.
Procedure
 A saturated red object was placed at the line of sight about five feet away from the viewer
 The object was gauzed at for 5 minutes and then removed.
Results
After the removal of the red object, a faint green color was observed at around the place where
the object was.
Discussion
The cones, the cells of the retina that are responsible for the color vision are joined together in
opposing pairs as per the mentioned above but only one con of the opposing pairs can form a
signal in the brain at a time (Zrenner, 2012). After exposing the ganglion cells of the cons to one
of the opposing colors, the ganglion cells become fatigued while those of the other opposing
color in the pair remains fresh. Therefore, after removal of the color to expose a background of a
different color, an afterimage of the opposing color is formed at the brain.
In this case, the red color was stared at for 30 minutes making the red color ganglion cells
become fatigued. Therefore, after the removal of the red object, a green afterimage, which is the
opposing color is seen.

ILLUMINATION 6
References
Zrenner, E. (2012). Neurophysiological aspects of color vision in primates: Comparative studies
on simian retinal ganglion cells and the human visual system (Vol. 9). Springer Science
& Business Media.
Reuter, T. (2011). Fifty years of dark adaptation 1961–2011. Vision research, 51(21-22), 2243-
2262.