Dynamic Range of Human Lightness Perception

Supplemental Material


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Induction Procedure

PRE-TEST:

Before the observer enters the room, turn the lamp on, remove the black felt covering the color palette, and place test block #2 in the left-hand chamber of the box, in the location marked "1" (see matching booth diagram below; the bottom right corner of the square should fit into the v-shaped mark).

Before the observers sit down, ask them not to touch any of the blocks until instructed to do so. Give the observer the following instructions:

In our experiments, we'll be asking you to judge the color appearance of painted surfaces, or of simulations of such surfaces. Before we start the main experiment, we'd like to have you do some simple matches so you get the idea of the type of judgments we'd like you to make.

Only one surface (point to the painted surface) of this block has been painted. Imagine that we need to pick the same color of paint in order to paint the rest of the block. The matching paint color is somewhere on this palette. So your task is to pick the square that appears to have same paint as the painted surface on the block. Please point to the square in the palette that corresponds to the matching paint. Take as long as you want to make your choice, but please do not touch the block or the palette. After you finish doing this for this block, we will do the same thing for one more block.

After the observer indicates the square, mark the square position (row, column) in the answer sheet, ask them to close their eyes while you remove the first test block and place test block #2 in the location marked "2". For this position, the bottom left corner of the block should fit in the v-shaped mark.

FAMILIARITY:

Cover up the test palette with the black felt. Put the three familiarity blocks on the table. Now tell the observer the following:

Now that you have performed a few matches, here are three blocks to examine. You can touch them or move them anywhere on the table. As you look at any of the blocks, you may notice that the amount of light reflected from the block appears to change as you move it or rotate it with respect to the light source. On the other hand, the block itself isn't changing as you move it - the paint on the blocks and therefore the fraction of light they reflect is staying the same. I'd like you to examine the blocks now and get a sense of how the amount of light reflected to your eye appears to change as you move or rotate each block, while realizing at the same time that the reflectance of the block itself is constant. Take as long as you like, and let me know when you are done. Wait until observer indicates he or she is done, then take the three blocks away and place them in the box with the rest of the blocks.

POST-TEST:

Tell the observer that you will now perform some more matches, just as before:

Again, the task is to judge the reflectance of the blocks and palette squares (that is, how the paint appears) rather than the amount of light that appears to reflect from them.

Ask the observer to close their eyes while you place the next test block in the correct location and remove the black felt from the palette. Repeat the testing procedure (asking them to mark the corresponding match in the grid of the palette square) for the remaining blocks in the following order:

3) BLOCK: 3 LOCATION: 4
4) BLOCK: 1 LOCATION: 3
5) BLOCK: 1 LOCATION: 1
6) BLOCK: 3 LOCATION: 2
7) BLOCK: 2 LOCATION: 3
8) BLOCK: 1 LOCATION: 4
9) BLOCK: 3 LOCATION: 3
10) BLOCK: 1 LOCATION: 2
11) BLOCK: 3 LOCATION: 1
12) BLOCK: 2 LOCATION: 4

For each trial, note the observers response (row/column in the palette) in the response sheet for that trial.

Munsell
Munsell
Diagram of the left chamber of the matching booth with block locations marked. Photograph of the matching booth.