diff --git a/changelog.txt b/changelog.txt
index 671587b..377fc42 100644
--- a/changelog.txt
+++ b/changelog.txt
@@ -79,7 +79,11 @@ add: r_rtColorFormat <0|1|2> (default: 0) selects the color format for render ta
   r_rtColorFormat 0 = R8G8B8A8
   r_rtColorFormat 1 = R10G10B10A2
   r_rtColorFormat 2 = R16G16B16A16
-  
+
+add: r_lightmapGreyscale <0.0 to 1.0> (default: 0) to control how monochromatic the lightmaps look
+  r_lightmapGreyscale 0 = full color (nothing done)
+  r_lightmapGreyscale 1 = completely monochrome
+
 add: r_mapBrightness now works on q3map2's external lightmap atlas images
 
 add: the renderer can now batch surfaces with different (but sufficiently similar) shaders
diff --git a/code/renderer/tr_bsp.cpp b/code/renderer/tr_bsp.cpp
index beac135..e26d3df 100644
--- a/code/renderer/tr_bsp.cpp
+++ b/code/renderer/tr_bsp.cpp
@@ -41,13 +41,20 @@ static int lightmapsPerAtlas;
 
 static void R_ColorShiftLightingBytesRGB( const byte* in, byte* out )
 {
-	const int scale16 = (int)( r_mapBrightness->value * 65536.0f );
-
 	// scale based on brightness
+	const int scale16 = (int)( r_mapBrightness->value * 65536.0f );
 	int r = ( (int)in[0] * scale16 ) >> 16;
 	int g = ( (int)in[1] * scale16 ) >> 16;
 	int b = ( (int)in[2] * scale16 ) >> 16;
 
+	// desaturate by moving the channels towards the grey "midpoint"
+	// credit for the following snippet goes to Jakub 'kubaxvx' Matraszek
+	const int grey = (r + g + b) / 3; // could use the Rec. 601 or 709 coefficients instead
+	const int greyscale16 = (int)( r_lightmapGreyscale->value * 65536.0f );
+	r = ( ( r << 16 ) + greyscale16 * ( grey - r ) ) >> 16;
+	g = ( ( g << 16 ) + greyscale16 * ( grey - g ) ) >> 16;
+	b = ( ( b << 16 ) + greyscale16 * ( grey - b ) ) >> 16;
+	
 	// normalize by color instead of saturating to white
 	if ( ( r | g | b ) > 255 ) {
 		int max;
diff --git a/code/renderer/tr_init.cpp b/code/renderer/tr_init.cpp
index e88e5d2..9f9f056 100644
--- a/code/renderer/tr_init.cpp
+++ b/code/renderer/tr_init.cpp
@@ -60,6 +60,7 @@ cvar_t	*r_drawworld;
 cvar_t	*r_speeds;
 cvar_t	*r_fullbright;
 cvar_t	*r_lightmap;
+cvar_t	*r_lightmapGreyscale;
 cvar_t	*r_novis;
 cvar_t	*r_nocull;
 cvar_t	*r_nocurves;
@@ -389,6 +390,7 @@ static const cvarTableItem_t r_cvars[] =
 	{ &r_subdivisions, "r_subdivisions", "1", CVAR_ARCHIVE | CVAR_LATCH, CVART_FLOAT, "1", "64", help_r_subdivisions },
 	{ &r_fullbright, "r_fullbright", "0", CVAR_ARCHIVE | CVAR_LATCH, CVART_BOOL, NULL, NULL, help_r_fullbright },
 	{ &r_lightmap, "r_lightmap", "0", CVAR_ARCHIVE | CVAR_LATCH, CVART_BOOL, NULL, NULL, help_r_lightmap },
+	{ &r_lightmapGreyscale, "r_lightmapGreyscale", "0", CVAR_ARCHIVE | CVAR_LATCH, CVART_FLOAT, "0", "1", "how monochrome the lightmap looks" },
 	{ &r_softSprites, "r_softSprites", "1", CVAR_ARCHIVE | CVAR_LATCH, CVART_BOOL, NULL, NULL, help_r_softSprites },
 	{ &r_gpuMipGen, "r_gpuMipGen", "1", CVAR_ARCHIVE | CVAR_LATCH, CVART_BOOL, NULL, NULL, help_r_gpuMipGen },
 	{ &r_alphaToCoverage, "r_alphaToCoverage", "1", CVAR_ARCHIVE | CVAR_LATCH, CVART_BOOL, NULL, NULL, help_r_alphaToCoverage },
diff --git a/code/renderer/tr_local.h b/code/renderer/tr_local.h
index e6d0a8e..bcc4526 100644
--- a/code/renderer/tr_local.h
+++ b/code/renderer/tr_local.h
@@ -982,6 +982,7 @@ extern cvar_t	*r_gamma;
 extern cvar_t	*r_greyscale;
 extern cvar_t	*r_noiseScale;			// the strength of the dithering noise
 extern cvar_t	*r_lightmap;			// render lightmaps only
+extern cvar_t	*r_lightmapGreyscale;	// how monochrome the lightmap looks
 extern cvar_t	*r_fullbright;			// avoid lightmap pass
 extern cvar_t	*r_softSprites;			// draws certain surfaces as depth particles
 extern cvar_t	*r_gpuMipGen;			// uses GPU-side mip-map generation