Our experimental results show that the Olympus D-220L digital camera uses a gray world assumption-based color-balancing algorithm, and not one based on the perfect reflector assumption. As my Matlab simulation shows, indiscriminate application of the gray world assumption often leads to unacceptable results. We have evidence from our analysis of the blue gray world test pattern that the camera, before it color-balances, actually tweaks its scale factors depending on the color distribution of the raw image.
Additional experiments that I would have liked to carry out include taking more test pattern pictures to study in greater detail how the camera is tweaking its scale factors. My hypothesis is that the camera will eventually suppress its color-balancing algorithm once the yellowishness of the test pattern goes beyond a certain threshold. We could test this by varying the test pattern's red and green multiplicative factor smoothly from 1 to 2, and measuring the camera's scale factors from the gray control patches. We should also repeat this experiment for test patterns that are predominantly greenish, reddish, etc..