ECE 178 WINTER 2003
DUE: January 17, 2003.
Note: The TA will go over the MATLAB exercise during the discussion on Friday, Jan 10.
READING: Chapter 2.1-2.3
* You do not need to submit solutions for problems marked with *. Clearly state any assumptions you make in solving the problems.
1. Problem 2.1*
2. Problem 2.3*
3. Problem 2.4
4. Problem 2.6*
5. Problem 2.10
6. MATLAB: Read the section on Brightness Adaptation in Chapter 2. The human visual system is extremely good at adapting to a wide range of brightness values--of the order of 10^10. However, it can not discriminate all these values simultaneously. It adapts to the ambient intensity and given the background brightness, can only discriminate a small range of values. READ section 2.1.
In the following programming assignment, which is actually quite a bit of fun, you will explore one variation of this adaptation. Ideally, I would like you to generate a plot similar to Figure 2.6 (typical Weber ratio plot). However, you are constrained by the experimental set-up available. Instead, we will fix the background intensity and vary continuously (we are, however, limited to a step-size of ONE gray level in the experiment below) the other intensity till you perceive the two-intensity pattern. Implement the following using MATLAB.
1. Create a square image of size 256x256 pixels. Fill the image with constant gray level value I=0.
2. Now create a center square, which is 10 pixels from the sides of the exterior square, having an intensity level I'=I+dx.
3. Start with dx=0; keep increasing dx till the center square just becomes perceivable to you. Let this value be Dx.
4. repeat steps 2 and 3 for this newly generated square by starting with I=I+DX and generating an inner square with a new intensity value. Continue this till I=255 (most computer displays do not display more than 256 shades of gray.)
You final image will look similar to the one below (the number of gray levels could be higher or lower, depending on your monitor!).
How many different shades of gray you perceive?
You need to present to the TA the following:
(a) a brief report including your final figure.
(b) the MATLAB code you used to run the experiment and generate the figure.
(c) (optional; strongly encouraged) show a demonstration to the TA as to how you carried out the experiment.