Stimuli subtended 16 x 12 visual degrees, whereas the window size was 6 x 4.6 degrees. The window was always centered on the fixation position. In the examples below the subject is fixating the small boat. The low-pass filter removed all spatial frequencies above 1 cycl./degr. The high-pass filter removed all frequencies below 3 cycl./degr., but maintained the static Fourier component (i.e. the average grey level). Within the window the normal, full-frequency stimulus appeared.