(1) Press UpArrow/DownArrow key to increase/decrease the brightness of the bottom half-field.
       Note: don't look  close to the screen, and leave some time (about 1 second) after each keypress.
(2) Press LeftArrow key after a best match is reached, when the line between the two half-fields is least visible.
Note: You can run the test with individual cololr channels by checking R, G, or B.
(3) Repeat the two steps until the measured gamma curve shows up.
(4) Press Esc key (or click the Quit button) to close current page.