BRIGHTNESS INDENTION - A NOVEL COMPRESSION MECHANISM IN THE LUMINANCEBRIGHTNESS MAPPING

In a previous study, Schouten and Blommaert (1995) explicitly showed t hat brightness constancy implies a substantial compression in the lumi nance-brightness mapping. Here it is argued that additional compressio n mechanisms are required for scenes with large luminance ranges, To t race these, a series of experiments was conducted which involved expan sion of the luminance range. We used a simple spatial configuration co nsisting of a disk on a contourless homogeneous surround (Ganzfeld). T he contrast between the disk and Ganzfeld acted as the independent var iable, while the size of the disk was parametrically varied. Sequentia l dichoptical brightness matches with a reference were carried out for both the disk and the surround, The results reveal a compression mech anism which we term brightness indention. This indention, which has no t previously been reported in the literature, only occurs if the Ganzf eld is less luminous than the disk, and it takes the form of a brightn ess decrease of the immediate surroundings of the disk.