These images use whites that are purely achromatic (red = green = blue), which is why they are not as brown or yellow as those of other people in the class.
(May be off by a factor of pi here somewhere . . . )
4 samples/pixel, 4 shadow rays/hit, 20% chance of absorbing indirect ray at each step.

4 samples/pixel, 4 shadow rays/hit, 10% chance of absorbing indirect ray at each step.

8 samples/pixel, 8 shadow rays/hit, 20% chance of absorbing indirect ray at each step.

8 samples/pixel, 8 shadow rays/hit, 10% chance of absorbing indirect ray at each step.
