Lesson Plan 14

Light, Vision and Digital Images

Lesson Title	Light, Vision and Digital Images – Light and Perception
Duration	2 classes (3 hours) [This topic could easily be expanded to 3 or more classes]
Synopsis	The students will learn the physical properties of light and be introduced to the biophysics of human vision. They will then learn how images are represented digitally, as well as stored and displayed on computers.
Description of Class	This is a series of lecture classes in which the students first learn the scientific principles behind light and human vision and then learn the basic mathematical and computer science principles used in representing, storing and displaying digital images using computer systems. Lastly the students learn the characteristics of different digital image file formats and compression schemes.
Primary Educational Objective	The students will learn that light is a form of electromagnetic radiation that can be described as both a wave and a particle. The students will learn the properties of visible light, such as wavelength and speed, and where visible light fits in the electromagnetic spectrum. The students will gain an understanding of the properties of reflection, refraction and absorption, as well as how colors are created by the absorption, reflection and transmission of various wavelengths, i.e. the spectral properties of materials. The students will learn how (low-level) human vision works, including the anatomy of the eye, the properties and specialized functions of the rod and cone cells in the retina, the fundamentals of the biochemical process of photo-excitation that occurs in those cells, and the process of neural signaling. The students will gain an understanding of the relationship between the human visual system and additive and subtractive color mixing. The students will be exposed to the complexities of human perception, including such properties as retinal fatigue and flicker fusion. They will learn the role that flicker fusion plays in film and video technologies. The principle underlying the representation of color as a triad of red, green and blue intensities is explained, as is the representation of an image by a matrix of individual color elements (i.e. pixels). The digital representation and storage of images on computer systems in a variety of formats is presented. Finally the students will learn how the hardware components that comprise a digital display system are organized and function.
Additional Concepts and Skills
Assessment	The students are asked to identify the approximate wavelength of various colors to demonstrate their understanding of the relationship between wavelengths and colors. The students are asked to determine the frequency given a wavelength and vice-versa. The students are asked to mix various colors by combining red, green and blue light.
Classroom Activities	The materials are presented in lecture format using the provided PowerPoint slides. The lecture begins with a review of sound waves and hearing, as well as a recap and expansion on the materials from Lesson 5 in which sine waves are described. The analogies between sound/hearing and light/seeing are carried throughout the lectures. Light is then presented as an electromagnetic force and its properties, such as frequency and speed through a medium given. Comparisons are made with sound waves. The notion that light can also be considered as a particle (i.e. photon) is presented. The interaction of light with materials is presented and the processes of absorption, reflection and refraction are described. Finally a segue is made to the perception of light by demonstrating the additive properties of light (e.g. combining red and green light results in the perception of yellow) and asking how this is possible. In the second half of this lesson, the human visual system is explained, starting with the anatomy of the eye and proceeding through the biochemical response in the retina which results in neural firings. The relationship between color cone cells in the retina and our perception of combinations of wavelength (i.e. primary color mixing) is explained. The last segment of the lesson focuses on the digital representation of an image as a two dimensional array (matrix) of color values. The properties of various file formats, such as .gif and .jpg, are explored.
Homework Assignments	TBD
Lecture Materials	Lecture materials are available as a Power Point presentation
Reference Materials	TBD
Prerequisites (this course)	Digital Media Part I – Digital Audio Corel I – Creating and using digital images
Related Topics	Characterization of electromagnetic waves. Dual nature of light as a wave and a particle. Absorption, reflection, refraction, and interference of waves. Human anatomy/sensory systems. Cell response to stimuli. Neurons and neural signaling. Photo-excitation/electron energy states/electro-chemical reactions. Proteins and other organic structures. Properties of electronic display systems (e.g. computer and television monitors) Functional components of computer systems. Binary representation (radix systems) Analog and digital conversion/sampling and quantization Creation and use of multi-media. Conversion of computer media file formats. Color mixing/color theory. Film and video animation.
Technology Requirements	None