p078fig02.29 How the adaptation level is chosen to enable sufficiently distinct inputs to activate their cells.<BR>||  Weber Law and adaptation level.<TABLE border="1"><TR><TD>xi = </td><TD>(B + C)*I/(A + I)* </td><TD>[θi </td><TD>-C/(B + C)]</td></tr><TR><TD></td><TD>Weber Law </td><TD>Reflectance </td><TD>Adaptation level</td></tr></table>V(+) >> V(-) ⇒ B >> C ⇒ C/(B + C) << 1<BR>Adaptation level theory (Zeiler 1963).