diff --git a/ChangeLog b/ChangeLog
index 00a70d23..45886456 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -4,6 +4,7 @@
   constant image
 - add new_from_image() to Python as well
 - slight change to cpp new_from_image() to match py/C behaviour
+- vips_conv(), vips_compass(), vips_convsep() default to FLOAT precision
 
 23/4/17 started 8.5.5
 - doc polishing
diff --git a/TODO b/TODO
index 95698e30..989041b5 100644
--- a/TODO
+++ b/TODO
@@ -1,3 +1,5 @@
+- vips_compass() needs docs
+
 - cpp bandjoin should use bandjoin_const() where possibel ... currently 
   uses new_from_image
 
diff --git a/libvips/conversion/smartcrop.c b/libvips/conversion/smartcrop.c
index be5a67e9..8c04eb76 100644
--- a/libvips/conversion/smartcrop.c
+++ b/libvips/conversion/smartcrop.c
@@ -193,8 +193,12 @@ vips_smartcrop_attention( VipsSmartcrop *smartcrop,
 	/* Sobel edge-detect on L.
 	 */
 	if( vips_extract_band( t[1], &t[2], 0, NULL ) ||
-		vips_conv( t[2], &t[3], t[21], NULL ) ||
-		vips_conv( t[2], &t[4], t[22], NULL ) ||
+		vips_conv( t[2], &t[3], t[21], 
+			"precision", VIPS_PRECISION_INTEGER,
+			NULL ) ||
+		vips_conv( t[2], &t[4], t[22], 
+			"precision", VIPS_PRECISION_INTEGER,
+			NULL ) ||
 		vips_abs( t[3], &t[5], NULL ) ||
 		vips_abs( t[4], &t[6], NULL ) ||
 		vips_add( t[5], t[6], &t[7], NULL ) )
diff --git a/libvips/convolution/compass.c b/libvips/convolution/compass.c
index f7f01870..bc140a76 100644
--- a/libvips/convolution/compass.c
+++ b/libvips/convolution/compass.c
@@ -2,6 +2,9 @@
  *
  * 23/10/13	
  * 	- from vips_conv()
+ * 8/5/17
+ *      - default to float ... int will often lose precision and should not be
+ *        the default
  */
 
 /*
@@ -172,7 +175,7 @@ vips_compass_class_init( VipsCompassClass *class )
 		_( "Convolve with this precision" ),
 		VIPS_ARGUMENT_OPTIONAL_INPUT, 
 		G_STRUCT_OFFSET( VipsCompass, precision ), 
-		VIPS_TYPE_PRECISION, VIPS_PRECISION_INTEGER ); 
+		VIPS_TYPE_PRECISION, VIPS_PRECISION_FLOAT ); 
 
 	VIPS_ARG_INT( class, "layers", 204, 
 		_( "Layers" ), 
@@ -196,7 +199,7 @@ vips_compass_init( VipsCompass *compass )
 	compass->times = 2;
 	compass->angle = VIPS_ANGLE45_D90;
 	compass->combine = VIPS_COMBINE_MAX;
-	compass->precision = VIPS_PRECISION_INTEGER;
+	compass->precision = VIPS_PRECISION_FLOAT;
 	compass->layers = 5;
 	compass->cluster = 1;
 }
diff --git a/libvips/convolution/conv.c b/libvips/convolution/conv.c
index 1a49290c..1be0d46f 100644
--- a/libvips/convolution/conv.c
+++ b/libvips/convolution/conv.c
@@ -2,6 +2,9 @@
  *
  * 12/8/13	
  * 	- from vips_hist_cum()
+ * 8/5/17
+ * 	- default to float ... int will often lose precision and should not be
+ * 	  the default
  */
 
 /*
@@ -137,7 +140,7 @@ vips_conv_class_init( VipsConvClass *class )
 		_( "Convolve with this precision" ),
 		VIPS_ARGUMENT_OPTIONAL_INPUT, 
 		G_STRUCT_OFFSET( VipsConv, precision ), 
-		VIPS_TYPE_PRECISION, VIPS_PRECISION_INTEGER ); 
+		VIPS_TYPE_PRECISION, VIPS_PRECISION_FLOAT ); 
 
 	VIPS_ARG_INT( class, "layers", 104, 
 		_( "Layers" ), 
@@ -158,7 +161,7 @@ vips_conv_class_init( VipsConvClass *class )
 static void
 vips_conv_init( VipsConv *conv )
 {
-	conv->precision = VIPS_PRECISION_INTEGER;
+	conv->precision = VIPS_PRECISION_FLOAT;
 	conv->layers = 5;
 	conv->cluster = 1;
 }
@@ -187,22 +190,23 @@ vips_conv_init( VipsConv *conv )
  *
  * where scale and offset are part of @mask. 
  *
+ * By default, @precision is 
+ * #VIPS_PRECISION_FLOAT. The output image 
+ * is always #VIPS_FORMAT_FLOAT unless @in is #VIPS_FORMAT_DOUBLE, in which case
+ * @out is also #VIPS_FORMAT_DOUBLE. 
+ *
  * If @precision is #VIPS_PRECISION_INTEGER, then 
  * elements of @mask are converted to
  * integers before convolution, using rint(),
  * and the output image 
  * always has the same #VipsBandFormat as the input image. 
  *
- * For #VIPS_FORMAT_UCHAR images, vips_conv() uses a fast vector path based on
+ * For #VIPS_FORMAT_UCHAR images and #VIPS_PRECISION_INTEGER @precision, 
+ * vips_conv() uses a fast vector path based on
  * fixed-point arithmetic. This can produce slightly different results. 
  * Disable the vector path with `--vips-novector` or `VIPS_NOVECTOR` or
  * vips_vector_set_enabled().
  *
- * If @precision is #VIPS_PRECISION_FLOAT then the convolution is performed
- * with floating-point arithmetic. The output image 
- * is always #VIPS_FORMAT_FLOAT unless @in is #VIPS_FORMAT_DOUBLE, in which case
- * @out is also #VIPS_FORMAT_DOUBLE. 
- *
  * If @precision is #VIPS_PRECISION_APPROXIMATE then, like
  * #VIPS_PRECISION_INTEGER, @mask is converted to int before convolution, and 
  * the output image 
diff --git a/libvips/convolution/convsep.c b/libvips/convolution/convsep.c
index 3ae4fbf1..33f95008 100644
--- a/libvips/convolution/convsep.c
+++ b/libvips/convolution/convsep.c
@@ -2,6 +2,9 @@
  *
  * 23/10/13	
  * 	- from vips_convsep()
+ * 8/5/17
+ *      - default to float ... int will often lose precision and should not be
+ *        the default
  */
 
 /*
@@ -128,7 +131,7 @@ vips_convsep_class_init( VipsConvsepClass *class )
 		_( "Convolve with this precision" ),
 		VIPS_ARGUMENT_OPTIONAL_INPUT, 
 		G_STRUCT_OFFSET( VipsConvsep, precision ), 
-		VIPS_TYPE_PRECISION, VIPS_PRECISION_INTEGER ); 
+		VIPS_TYPE_PRECISION, VIPS_PRECISION_FLOAT ); 
 
 	VIPS_ARG_INT( class, "layers", 204, 
 		_( "Layers" ), 
@@ -149,7 +152,7 @@ vips_convsep_class_init( VipsConvsepClass *class )
 static void
 vips_convsep_init( VipsConvsep *convsep )
 {
-	convsep->precision = VIPS_PRECISION_INTEGER;
+	convsep->precision = VIPS_PRECISION_FLOAT;
 	convsep->layers = 5;
 	convsep->cluster = 1;
 }
diff --git a/libvips/convolution/sharpen.c b/libvips/convolution/sharpen.c
index a95242fb..ab4c78ac 100644
--- a/libvips/convolution/sharpen.c
+++ b/libvips/convolution/sharpen.c
@@ -264,7 +264,9 @@ vips_sharpen_build( VipsObject *object )
 	 */
 	if( vips_extract_band( in, &args[0], 0, NULL ) ||
 		vips_extract_band( in, &t[3], 1, "n", in->Bands - 1, NULL ) ||
-		vips_convsep( args[0], &args[1], t[1], NULL ) )
+		vips_convsep( args[0], &args[1], t[1], 
+			"precision", VIPS_PRECISION_INTEGER,
+			NULL ) )
 		return( -1 );
 
 	/* Set demand hints. FATSTRIP is good for us, as THINSTRIP will cause
diff --git a/libvips/deprecated/vips7compat.c b/libvips/deprecated/vips7compat.c
index db23ec21..9420a608 100644
--- a/libvips/deprecated/vips7compat.c
+++ b/libvips/deprecated/vips7compat.c
@@ -2283,6 +2283,7 @@ im_compass( VipsImage *in, VipsImage *out, INTMASK *mask )
 	if( vips_compass( in, &t2, t1, 
 		"times", 8, 
 		"angle", VIPS_ANGLE45_D45, 
+		"precision", VIPS_PRECISION_INTEGER,
 		NULL ) ) {
 		g_object_unref( t1 );
 		return( -1 );
@@ -2308,6 +2309,7 @@ im_lindetect( IMAGE *in, IMAGE *out, INTMASK *mask )
 	if( vips_compass( in, &t2, t1, 
 		"times", 4, 
 		"angle", VIPS_ANGLE45_D45, 
+		"precision", VIPS_PRECISION_INTEGER,
 		NULL ) ) {
 		g_object_unref( t1 );
 		return( -1 );
@@ -2334,6 +2336,7 @@ im_gradient( IMAGE *in, IMAGE *out, INTMASK *mask )
 		"times", 2, 
 		"angle", VIPS_ANGLE45_D90, 
 		"combine", VIPS_COMBINE_SUM, 
+		"precision", VIPS_PRECISION_INTEGER,
 		NULL ) ) {
 		g_object_unref( t1 );
 		return( -1 );
@@ -2364,6 +2367,7 @@ im_convsep( IMAGE *in, IMAGE *out, INTMASK *mask )
 		im_imask2vips( mask, t1 ) )
 		return( -1 );
 	if( vips_convsep( in, &t2, t1, 
+		"precision", VIPS_PRECISION_INTEGER,
 		NULL ) ) {
 		g_object_unref( t1 );
 		return( -1 );
@@ -2393,9 +2397,7 @@ im_convsep_f( IMAGE *in, IMAGE *out, DOUBLEMASK *mask )
 	if( !(t1 = vips_image_new()) ||
 		im_mask2vips( mask, t1 ) )
 		return( -1 );
-	if( vips_convsep( in, &t2, t1, 
-		"precision", VIPS_PRECISION_FLOAT,
-		NULL ) ) {
+	if( vips_convsep( in, &t2, t1, NULL ) ) {
 		g_object_unref( t1 );
 		return( -1 );
 	}
@@ -2561,12 +2563,18 @@ im_contrast_surface( IMAGE *in, IMAGE *out, int half_win_size, int spacing )
 		for( x = 0; x < size; x++ )
 			*VIPS_MATRIX( t[8], x, y ) = 1.0;
 
-	if( vips_conv( in, &t[2], t[0], NULL ) ||
-		vips_conv( in, &t[3], t[1], NULL ) ||
+	if( vips_conv( in, &t[2], t[0], 
+			"precision", VIPS_PRECISION_INTEGER,
+			NULL ) ||
+		vips_conv( in, &t[3], t[1], 
+			"precision", VIPS_PRECISION_INTEGER,
+			NULL ) ||
 		vips_abs( t[2], &t[4], NULL ) ||
 		vips_abs( t[3], &t[5], NULL ) ||
 		vips_add( t[4], t[5], &t[6], NULL ) ||
-		vips_conv( t[6], &t[7], t[8], NULL ) ||
+		vips_conv( t[6], &t[7], t[8], 
+			"precision", VIPS_PRECISION_INTEGER,
+			NULL ) ||
 		vips_subsample( t[7], &t[9], spacing, spacing, NULL ) ||
 		vips_image_write( t[9], out ) )
 		return( -1 ); 
diff --git a/libvips/histogram/hist_ismonotonic.c b/libvips/histogram/hist_ismonotonic.c
index ba0e735e..9a4b6986 100644
--- a/libvips/histogram/hist_ismonotonic.c
+++ b/libvips/histogram/hist_ismonotonic.c
@@ -90,7 +90,9 @@ vips_hist_ismonotonic_build( VipsObject *object )
 
 	/* We want >=128 everywhere, ie. no -ve transitions.
 	 */
-	if( vips_conv( ismonotonic->in, &t[1], t[0], NULL ) ||
+	if( vips_conv( ismonotonic->in, &t[1], t[0], 
+			"precision", VIPS_PRECISION_INTEGER,
+			NULL ) ||
 		vips_moreeq_const1( t[1], &t[2], 128, NULL ) ||
 		vips_min( t[2], &m, NULL ) )
 		return( -1 );
diff --git a/libvips/morphology/countlines.c b/libvips/morphology/countlines.c
index ec2b092c..7fbdc85b 100644
--- a/libvips/morphology/countlines.c
+++ b/libvips/morphology/countlines.c
@@ -92,7 +92,9 @@ vips_countlines_build( VipsObject *object )
 	case VIPS_DIRECTION_HORIZONTAL:
 		if( !(t[0] = vips_image_new_matrixv( 1, 2, -1.0, 1.0 )) ||
 			vips_moreeq_const1( in, &t[1], 128, NULL ) ||
-			vips_conv( t[1], &t[2], t[0], NULL ) ||
+			vips_conv( t[1], &t[2], t[0], 
+				"precision", VIPS_PRECISION_INTEGER,
+				NULL ) ||
 			vips_project( t[2], &t[3], &t[4], NULL ) ||
 			vips_avg( t[3], &nolines, NULL ) )
 			return( -1 ); 
@@ -101,7 +103,9 @@ vips_countlines_build( VipsObject *object )
 	case VIPS_DIRECTION_VERTICAL:
 		if( !(t[0] = vips_image_new_matrixv( 2, 1, -1.0, 1.0 )) ||
 			vips_moreeq_const1( in, &t[1], 128, NULL ) ||
-			vips_conv( t[1], &t[2], t[0], NULL ) ||
+			vips_conv( t[1], &t[2], t[0], 
+				"precision", VIPS_PRECISION_INTEGER,
+				NULL ) ||
 			vips_project( t[2], &t[3], &t[4], NULL ) ||
 			vips_avg( t[4], &nolines, NULL ) )
 			return( -1 );