diff --git a/libvips/conversion/composite.c b/libvips/conversion/composite.c
index ec67ed8d..a287c82d 100644
--- a/libvips/conversion/composite.c
+++ b/libvips/conversion/composite.c
@@ -75,19 +75,11 @@
  * VIPS_BLEND_MODE_XOR:
  * VIPS_BLEND_MODE_ADD:
  * VIPS_BLEND_MODE_SATURATE:
- * VIPS_BLEND_MODE_MULTIPLY:
- * VIPS_BLEND_MODE_SCREEN:
- * VIPS_BLEND_MODE_OVERLAY:
- * VIPS_BLEND_MODE_DARKEN:
- * VIPS_BLEND_MODE_LIGHTEN:
- * VIPS_BLEND_MODE_COLOUR_DODGE:
- * VIPS_BLEND_MODE_COLOUR_BURN:
- * VIPS_BLEND_MODE_HARD_LIGHT:
- * VIPS_BLEND_MODE_SOFT_LIGHT:
- * VIPS_BLEND_MODE_DIFFERENCE:
- * VIPS_BLEND_MODE_EXCLUSION:
  *
  * The various Porter-Duff blend modes. See vips_composite(), for example. 
+ *
+ * The PDF blend modes require channels all in [0, 1], so they only work
+ * for spaces like RGB where all channels have the same range. 
  */
 
 /* References:
@@ -248,6 +240,9 @@ G_DEFINE_TYPE( VipsComposite, vips_composite, VIPS_TYPE_CONVERSION );
  */
 
 #define BLEND_MULTIPLY( MODE, xR, aR, xA, aA, xB, aB, CODE ) { \
+	double t1; \
+	double t2; \
+	\
 	switch( MODE ) { \
 	case VIPS_BLEND_MODE_CLEAR: \
 		CODE( xR = 1 - aA ); \
@@ -258,7 +253,8 @@ G_DEFINE_TYPE( VipsComposite, vips_composite, VIPS_TYPE_CONVERSION );
 		break; \
 	\
 	case VIPS_BLEND_MODE_OVER: \
-		CODE( xR = (aA * xA + aB * xB * (1 - aA)) / aR ); \
+		t1 = aB * (1 - aA); \
+		CODE( xR = (aA * xA + t1 * xB) / aR ); \
 		break; \
 	\
 	case VIPS_BLEND_MODE_IN: \
@@ -278,7 +274,8 @@ G_DEFINE_TYPE( VipsComposite, vips_composite, VIPS_TYPE_CONVERSION );
 		break; \
 	\
 	case VIPS_BLEND_MODE_DEST_OVER: \
-		CODE( xR = (aB * xB + aA * xA * (1 - aB)) / aR ); \
+		t1 = aA * (1 - aB); \
+		CODE( xR = (aB * xB + t1 * xA) / aR ); \
 		break; \
 	\
 	case VIPS_BLEND_MODE_DEST_IN: \
@@ -294,7 +291,9 @@ G_DEFINE_TYPE( VipsComposite, vips_composite, VIPS_TYPE_CONVERSION );
 		break; \
 	\
 	case VIPS_BLEND_MODE_XOR: \
-		CODE( xR = (xA * aA * (1 - aB) + xB * aB * (1 - aA)) / aR ); \
+		t1 = aA * (1 - aB); \
+		t2 = aB * (1 - aA); \
+		CODE( xR = (t1 * xA + t2 * xB) / aR ); \
 		break; \
 	\
 	case VIPS_BLEND_MODE_ADD: \
@@ -302,7 +301,8 @@ G_DEFINE_TYPE( VipsComposite, vips_composite, VIPS_TYPE_CONVERSION );
 		break; \
 	\
 	case VIPS_BLEND_MODE_SATURATE: \
-		CODE( xR = (VIPS_MIN( aA, 1 - aB ) * xA + xB * aB) / aR ); \
+		t1 = VIPS_MIN( aA, 1 - aB ); \
+		CODE( xR = (t1 * xA + xB * aB) / aR ); \
 		break; \
 	\
 	default: \
@@ -312,6 +312,8 @@ G_DEFINE_TYPE( VipsComposite, vips_composite, VIPS_TYPE_CONVERSION );
 }
 
 #define BLEND_PREMULTIPLIED( MODE, xR, xA, aA, xB, aB, CODE ) { \
+	double t1; \
+	\
 	switch( MODE ) { \
 	case VIPS_BLEND_MODE_CLEAR: \
 		CODE( xR = 1 - aA ); \
@@ -366,7 +368,8 @@ G_DEFINE_TYPE( VipsComposite, vips_composite, VIPS_TYPE_CONVERSION );
 		break; \
 	\
 	case VIPS_BLEND_MODE_SATURATE: \
-		CODE( xR = VIPS_MIN( aA, 1 - aB ) * xA + xB ); \
+		t1 = VIPS_MIN( aA, 1 - aB ); \
+		CODE( xR = t1 * xA + xB ); \
 		break; \
 	\
 	default: \
diff --git a/libvips/include/vips/conversion.h b/libvips/include/vips/conversion.h
index dc70ef26..dcf33495 100644
--- a/libvips/include/vips/conversion.h
+++ b/libvips/include/vips/conversion.h
@@ -104,17 +104,6 @@ typedef enum {
 	VIPS_BLEND_MODE_XOR,
 	VIPS_BLEND_MODE_ADD,
 	VIPS_BLEND_MODE_SATURATE,
-	VIPS_BLEND_MODE_MULTIPLY,
-	VIPS_BLEND_MODE_SCREEN,
-	VIPS_BLEND_MODE_OVERLAY,
-	VIPS_BLEND_MODE_DARKEN,
-	VIPS_BLEND_MODE_LIGHTEN,
-	VIPS_BLEND_MODE_COLOUR_DODGE,
-	VIPS_BLEND_MODE_COLOUR_BURN,
-	VIPS_BLEND_MODE_HARD_LIGHT,
-	VIPS_BLEND_MODE_SOFT_LIGHT,
-	VIPS_BLEND_MODE_DIFFERENCE,
-	VIPS_BLEND_MODE_EXCLUSION,
 	VIPS_BLEND_MODE_LAST
 } VipsBlendMode;
 
diff --git a/libvips/iofuncs/enumtypes.c b/libvips/iofuncs/enumtypes.c
index 17751d96..eda87719 100644
--- a/libvips/iofuncs/enumtypes.c
+++ b/libvips/iofuncs/enumtypes.c
@@ -369,17 +369,6 @@ vips_blend_mode_get_type( void )
 			{VIPS_BLEND_MODE_XOR, "VIPS_BLEND_MODE_XOR", "xor"},
 			{VIPS_BLEND_MODE_ADD, "VIPS_BLEND_MODE_ADD", "add"},
 			{VIPS_BLEND_MODE_SATURATE, "VIPS_BLEND_MODE_SATURATE", "saturate"},
-			{VIPS_BLEND_MODE_MULTIPLY, "VIPS_BLEND_MODE_MULTIPLY", "multiply"},
-			{VIPS_BLEND_MODE_SCREEN, "VIPS_BLEND_MODE_SCREEN", "screen"},
-			{VIPS_BLEND_MODE_OVERLAY, "VIPS_BLEND_MODE_OVERLAY", "overlay"},
-			{VIPS_BLEND_MODE_DARKEN, "VIPS_BLEND_MODE_DARKEN", "darken"},
-			{VIPS_BLEND_MODE_LIGHTEN, "VIPS_BLEND_MODE_LIGHTEN", "lighten"},
-			{VIPS_BLEND_MODE_COLOUR_DODGE, "VIPS_BLEND_MODE_COLOUR_DODGE", "colour-dodge"},
-			{VIPS_BLEND_MODE_COLOUR_BURN, "VIPS_BLEND_MODE_COLOUR_BURN", "colour-burn"},
-			{VIPS_BLEND_MODE_HARD_LIGHT, "VIPS_BLEND_MODE_HARD_LIGHT", "hard-light"},
-			{VIPS_BLEND_MODE_SOFT_LIGHT, "VIPS_BLEND_MODE_SOFT_LIGHT", "soft-light"},
-			{VIPS_BLEND_MODE_DIFFERENCE, "VIPS_BLEND_MODE_DIFFERENCE", "difference"},
-			{VIPS_BLEND_MODE_EXCLUSION, "VIPS_BLEND_MODE_EXCLUSION", "exclusion"},
 			{VIPS_BLEND_MODE_LAST, "VIPS_BLEND_MODE_LAST", "last"},
 			{0, NULL, NULL}
 		};