it is based

system/camerad/cameras/real_debayer.cl

@@ -27,7 +27,7 @@ float3 color_correct(float3 rgb, int expo) {
   return -0.507089*exp(-12.54124638*x)+0.9655*powr(x,0.5)-0.472597*x+0.507089;
   #elif IS_OS
   float s = fmax(log2((float)expo), 6.0);
-  return clamp(log(1 + x*65536.0) * (0.43*s*s - 11.9*s + 110.0) - (0.96*s*s - 26.8*s + 248.0), 0.0, 255.0) / 255.0;
+  return clamp(log(64 + x*65472.0) * (0.43*s*s - 11.9*s + 110.0) - (0.96*s*s - 26.8*s + 248.0), 0.0, 255.0) / 255.0;
   #else
   // tone mapping params
   const float gamma_k = 0.75;