Figure 5.

Binocular luminance summation of luminance discs with asymmetric contour information. (A) A sample from Experiment 1 of equal-luminance increment contour when the two eyes view two discs without concentric circles, luminance increment (8 cd/m²) from a dark background (0.2 cd/m²). The thick black curve indicates the model prediction using the same LoG filter, contrast space weight function (CSWF), and flat CSF as in Experiment 1. Dashed black curve (overlapped with the thick black curve) indicates the prediction using the same LoG filter and CSWF as in Experiment 1, but using non-flat CSF in the model. Dashed magenta and green curves (also overlapped with the thick black curve) indicate the model predictions using a smaller or a larger LoG filter than that in Experiment 1, while using the same CSWF and flat CSF. Solid blue and red curves indicates the prediction using the same LoG filter and flat CSF but a different CSWF with a slower (blue) or more rapid (red) dropping rate in space weight when going away from the fovea. The dashed red curve (overlapped with the solid red curve) indicates the prediction using a rapid-dropping CSWF and a non-flat CSF while the LoG filter is the same as in Experiment 1. (B) Equal-luminance increment contour when the two eyes view two discs with a concentric circle only in one eye (e.g., LE) (Experiment 2a). The codes for model prediction curves are the same as in (A )(the dashed magenta curve is overlapped with the thick black curve). (C) Equal-luminance increment contour when the two eyes view two discs with circles at different locations of the disc in the two eyes. One eye's circle (e.g., LE's) is in the upper and the other eye's circle (e.g., RE's) is in the lower half of the disc, and the luminance inside the upper circle is the target luminance on which the brightness match was performed (Experiment 2b). The codes for model prediction curves are the same as in (A) (the dashed magenta and green curves are overlapped with the thick black curve). (D) The disc size effect on binocular luminance summation. One eye (e.g., RE) views the luminance, fixed at 72 cd/m², of a large square of 14° x 14° on the dark background (0.2 cd/m²), and the other eye (e.g., LE) views a central disc of variable size (1°, 3°, 5°, 7°, 9°, 11°, 13° in diameters), with luminance fixed at 12 cd/m², plus a surrounding square of 14° × 14°, with luminance fixed at 3.7 cd/m², on the dark background (0.2 cd/m²). The luminance of the reference (same incremental luminance in both eyes) was adjusted to match the brightness of the test disc region. The binocularly matched luminance of the central disc was measured and plotted as a function of the disc diameter. The codes for model prediction curves are the same as in (A) (the dashed magenta and green curves are overlapped with the thick black curve).