diff --git a/TODO b/TODO
index 462018cb..0ae8d84d 100644
--- a/TODO
+++ b/TODO
@@ -12,8 +12,6 @@
 
   note on memuse page
 
-- add vips_gamma(), see rad etc. 
-
 - do conv and morph quickly as simple wrappers over the vips7 operations
 
 - add vips_gaussian_blur() with approx / int / float precision, maybe
diff --git a/libvips/conversion/Makefile.am b/libvips/conversion/Makefile.am
index 8e3cb0af..9b0e786c 100644
--- a/libvips/conversion/Makefile.am
+++ b/libvips/conversion/Makefile.am
@@ -4,7 +4,7 @@ libconversion_la_SOURCES = \
 	conversion.c \
 	pconversion.h \
 	tilecache.c \
-	gammacorrect.c \
+	gamma.c \
 	sequential.c \
 	flatten.c \
 	cache.c \
diff --git a/libvips/conversion/conversion.c b/libvips/conversion/conversion.c
index edb5c3e8..980cfe51 100644
--- a/libvips/conversion/conversion.c
+++ b/libvips/conversion/conversion.c
@@ -232,7 +232,7 @@ vips_conversion_operation_init( void )
 #endif /*HAVE_PANGOFT2*/
 	extern GType vips_xyz_get_type( void ); 
 	extern GType vips_falsecolour_get_type( void ); 
-	extern GType vips_gammacorrect_get_type( void ); 
+	extern GType vips_gamma_get_type( void ); 
 
 	vips_copy_get_type();
 	vips_tile_cache_get_type(); 
@@ -270,7 +270,7 @@ vips_conversion_operation_init( void )
 #endif /*HAVE_PANGOFT2*/
 	vips_xyz_get_type(); 
 	vips_falsecolour_get_type(); 
-	vips_gammacorrect_get_type(); 
+	vips_gamma_get_type(); 
 }
 
 /* The common part of most binary conversion
diff --git a/libvips/conversion/gammacorrect.c b/libvips/conversion/gamma.c
similarity index 98%
rename from libvips/conversion/gammacorrect.c
rename to libvips/conversion/gamma.c
index 93aa1e93..2063b7bb 100644
--- a/libvips/conversion/gammacorrect.c
+++ b/libvips/conversion/gamma.c
@@ -93,10 +93,10 @@ vips_gamma_build( VipsObject *object )
 		return( -1 );
 
 	scale = pow( vips_gamma_maxval[in->BandFmt], 
-			gamma->exponent ) / 
+			1.0 / gamma->exponent ) / 
 			vips_gamma_maxval[in->BandFmt];
 
-	if( in->BandFmt == VIPS_FORMAT_UCHAR &&
+	if( in->BandFmt == VIPS_FORMAT_UCHAR ||
 		in->BandFmt == VIPS_FORMAT_USHORT ) {
 		if( vips_identity( &t[0], 
 				"ushort", in->BandFmt == VIPS_FORMAT_USHORT,