Supplies: ruler, eraser, HB pencil and 8 1/2 x 14" white paper.

Instructions: Applying pressure with a pencil, create a tonal value scale (white and black at the ends of the scale and four or more gradations between the ends) on the far left of the paper as shown in stage #1. Then lightly draw six frames; squares with a smaller square in each one. Shade the inner square of the first four frames with the same medium grey tone as shown in stage #1.
In stage #2 shade the area surrounding the inner square of the 2nd and 5th frames with a tone slightly darker in value than that of the inner square of the 2nd frame. Then shade the area surrounding the inner square of the 3rd and 6th frames with a tone of a darker value (almost black) of the inner square of the 3rd frame. Compare the three inside squares of the top three frames. Notice the illusion that is created: the tonal value of the inner square appears to get lighter as the tonal value of the background gets darker. The background affects the value of the tone of the inner square.
In stage #3 shade the inner squares of the 5th and 6th frames to match the tonal value of the inner square of the 4th frame. As observed in stage #2, when the tonal value of the background becomes darker an illusion is created, which has the tonal value of the inner square appearing lighter. Increasing the tonal value of the inner squares of the 5trh and 6th frames will be required to make the tonal value of the inner squares appear equal.

Evaluation: The drawing should display the student's clear understanding of 1) a tonal value scale of pure white to black with each gradation's value between getting darker, 2) the illusion created by a background with a darker tonal value, and 3) how to alter the illusion by altering tonal value.