diff --git a/README b/README
index 58af58f7..7e4c19b3 100644
--- a/README
+++ b/README
@@ -181,7 +181,8 @@ New cvars
   r_ext_texture_filter_anisotropic  - anisotropic texture filtering
   r_zProj                           - distance of observer camera to projection
                                       plane in quake3 standard units
-  r_greyscale                       - render black and white images
+  r_greyscale                       - desaturate textures, useful for anaglyph,
+                                      supports values in the range of 0 to 1
   r_stereoEnabled                   - enable stereo rendering for techniques
                                       like shutter glasses (untested)
   r_anaglyphMode                    - Enable rendering of anaglyph images
diff --git a/code/qcommon/q_shared.h b/code/qcommon/q_shared.h
index a3935c91..56734dce 100644
--- a/code/qcommon/q_shared.h
+++ b/code/qcommon/q_shared.h
@@ -1307,4 +1307,7 @@ typedef enum _flag_status {
 #define CDCHKSUM_LEN 2
 
 
+#define LERP( a, b, w ) ( ( a ) * ( 1.0f - ( w ) ) + ( b ) * ( w ) )
+#define LUMA( red, green, blue ) ( 0.2126f * ( red ) + 0.7152f * ( green ) + 0.0722f * ( blue ) )
+
 #endif	// __Q_SHARED_H
diff --git a/code/renderer/tr_image.c b/code/renderer/tr_image.c
index c86e32a6..4dd12237 100644
--- a/code/renderer/tr_image.c
+++ b/code/renderer/tr_image.c
@@ -560,6 +560,27 @@ static void Upload32( unsigned *data,
 	scan = ((byte *)data);
 	samples = 3;
 
+	if( r_greyscale->integer )
+	{
+		for ( i = 0; i < c; i++ )
+		{
+			byte luma = LUMA(scan[i*4], scan[i*4 + 1], scan[i*4 + 2]);
+			scan[i*4] = luma;
+			scan[i*4 + 1] = luma;
+			scan[i*4 + 2] = luma;
+		}
+	}
+	else if( r_greyscale->value )
+	{
+		for ( i = 0; i < c; i++ )
+		{
+			float luma = LUMA(scan[i*4], scan[i*4 + 1], scan[i*4 + 2]);
+			scan[i*4] = LERP(scan[i*4], luma, r_greyscale->value);
+			scan[i*4 + 1] = LERP(scan[i*4 + 1], luma, r_greyscale->value);
+			scan[i*4 + 2] = LERP(scan[i*4 + 2], luma, r_greyscale->value);
+		}
+	}
+
 	if(lightMap)
 	{
 		if(r_greyscale->integer)
diff --git a/code/renderer/tr_init.c b/code/renderer/tr_init.c
index 8c0cf687..d28998ee 100644
--- a/code/renderer/tr_init.c
+++ b/code/renderer/tr_init.c
@@ -920,6 +920,7 @@ void R_Register( void )
 	r_stereoEnabled = ri.Cvar_Get( "r_stereoEnabled", "0", CVAR_ARCHIVE | CVAR_LATCH);
 	r_ignoreFastPath = ri.Cvar_Get( "r_ignoreFastPath", "1", CVAR_ARCHIVE | CVAR_LATCH );
 	r_greyscale = ri.Cvar_Get("r_greyscale", "0", CVAR_ARCHIVE | CVAR_LATCH);
+	ri.Cvar_CheckRange(r_greyscale, 0, 1, qfalse);
 
 	//
 	// temporary latched variables that can only change over a restart
diff --git a/code/renderer/tr_noise.c b/code/renderer/tr_noise.c
index af2f84e4..fca9eac6 100644
--- a/code/renderer/tr_noise.c
+++ b/code/renderer/tr_noise.c
@@ -31,8 +31,6 @@ Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 static float s_noise_table[NOISE_SIZE];
 static int s_noise_perm[NOISE_SIZE];
 
-#define LERP( a, b, w ) ( a * ( 1.0f - w ) + b * w )
-
 static float GetNoiseValue( int x, int y, int z, int t )
 {
 	int index = INDEX( ( int ) x, ( int ) y, ( int ) z, ( int ) t );
diff --git a/code/renderer/tr_shade.c b/code/renderer/tr_shade.c
index 33a7f2bf..2a53c97f 100644
--- a/code/renderer/tr_shade.c
+++ b/code/renderer/tr_shade.c
@@ -459,9 +459,18 @@ static void ProjectDlightTexture_altivec( void ) {
 		{
 			float luminance;
 			
-			luminance = (dl->color[0] * 255.0f + dl->color[1] * 255.0f + dl->color[2] * 255.0f) / 3;
+			luminance = LUMA(dl->color[0], dl->color[1], dl->color[2]) * 255.0f;
 			floatColor[0] = floatColor[1] = floatColor[2] = luminance;
 		}
+		else if(r_greyscale->value)
+		{
+			float luminance;
+			
+			luminance = LUMA(dl->color[0], dl->color[1], dl->color[2]) * 255.0f;
+			floatColor[0] = LERP(dl->color[0] * 255.0f, luminance, r_greyscale->value);
+			floatColor[1] = LERP(dl->color[1] * 255.0f, luminance, r_greyscale->value);
+			floatColor[2] = LERP(dl->color[2] * 255.0f, luminance, r_greyscale->value);
+		}
 		else
 		{
 			floatColor[0] = dl->color[0] * 255.0f;
@@ -612,10 +621,19 @@ static void ProjectDlightTexture_scalar( void ) {
 		if(r_greyscale->integer)
 		{
 			float luminance;
-			
-			luminance = (dl->color[0] * 255.0f + dl->color[1] * 255.0f + dl->color[2] * 255.0f) / 3;
+
+			luminance = LUMA(dl->color[0], dl->color[1], dl->color[2]) * 255.0f;
 			floatColor[0] = floatColor[1] = floatColor[2] = luminance;
 		}
+		else if(r_greyscale->value)
+		{
+			float luminance;
+			
+			luminance = LUMA(dl->color[0], dl->color[1], dl->color[2]) * 255.0f;
+			floatColor[0] = LERP(dl->color[0] * 255.0f, luminance, r_greyscale->value);
+			floatColor[1] = LERP(dl->color[1] * 255.0f, luminance, r_greyscale->value);
+			floatColor[2] = LERP(dl->color[2] * 255.0f, luminance, r_greyscale->value);
+		}
 		else
 		{
 			floatColor[0] = dl->color[0] * 255.0f;
@@ -964,11 +982,22 @@ static void ComputeColors( shaderStage_t *pStage )
 	if(r_greyscale->integer)
 	{
 		int scale;
+		for(i = 0; i < tess.numVertexes; i++)
+		{
+			scale = LUMA(tess.svars.colors[i][0], tess.svars.colors[i][1], tess.svars.colors[i][2]);
+ 			tess.svars.colors[i][0] = tess.svars.colors[i][1] = tess.svars.colors[i][2] = scale;
+		}
+	}
+	else if(r_greyscale->value)
+	{
+		float scale;
 		
 		for(i = 0; i < tess.numVertexes; i++)
 		{
-			scale = (tess.svars.colors[i][0] + tess.svars.colors[i][1] + tess.svars.colors[i][2]) / 3;
-			tess.svars.colors[i][0] = tess.svars.colors[i][1] = tess.svars.colors[i][2] = scale;
+			scale = LUMA(tess.svars.colors[i][0], tess.svars.colors[i][1], tess.svars.colors[i][2]);
+			tess.svars.colors[i][0] = LERP(tess.svars.colors[i][0], scale, r_greyscale->value);
+			tess.svars.colors[i][1] = LERP(tess.svars.colors[i][1], scale, r_greyscale->value);
+			tess.svars.colors[i][2] = LERP(tess.svars.colors[i][2], scale, r_greyscale->value);
 		}
 	}
 }