--- ray/src/common/tonemap.c	2021/05/04 21:50:54	3.51
+++ ray/src/common/tonemap.c	2022/01/15 16:57:46	3.54
@@ -1,5 +1,5 @@
 #ifndef lint
-static const char	RCSid[] = "$Id: tonemap.c,v 3.51 2021/05/04 21:50:54 greg Exp $";
+static const char	RCSid[] = "$Id: tonemap.c,v 3.54 2022/01/15 16:57:46 greg Exp $";
 #endif
 /*
  * Tone mapping functions.
@@ -95,7 +95,7 @@ tmSetSpace(			/* set input color space for conversions
 TMstruct	*tms,
 RGBPRIMP	pri,
 double	sf,
-MEM_PTR	dat
+void	*dat
 )
 {
 	static const char funcName[] = "tmSetSpace";
@@ -321,7 +321,9 @@ int	len
 				cmon[BLU] += d;
 			}
 		} else if (tms->flags & TM_F_BW) {
-			cmon[RED] = cmon[GRN] = cmon[BLU] = lum;
+			int	j = 3;
+			while (j--) cs[3*i+j] = tms->cdiv[j]/(TM_BRES>>8);
+			continue;
 		}
 		d = tms->clf[RED]*cmon[RED]/lum;
 		cs[3*i  ] = d>=.999f ? 255 : gamtab[(int)(1024.f*d)];
@@ -491,10 +493,10 @@ double	Ldmax
 	}
 	if (!histot)
 		returnErr(TM_E_TMFAIL);
-	threshold = histot/40 + 1;
+	threshold = histot/500 + 1;
 	Lwavg = tmLuminance( (double)sum / histot );
 					/* use linear tone mapping? */
-	if (tms->flags & TM_F_LINEAR || threshold < 4 ||
+	if (tms->flags & TM_F_LINEAR ||
 			tms->hbrmax - tms->hbrmin < TM_BRTSCALE*logLddyn)
 		goto linearmap;
 					/* clamp histogram */