diff --git a/changelog.txt b/changelog.txt
index d1d8b1b..2a21e50 100644
--- a/changelog.txt
+++ b/changelog.txt
@@ -1,10 +1,12 @@
 
 DD Mmm 17 - 1.49
 
-chg: r_brightness    <0.25..32> (default: 2) replaces r_overBrightBits
-     r_mapBrightness <0.25..32> (default: 4) replaces r_mapOverBrightBits
+chg: r_brightness    <0.25..32.0> (default: 2) replaces r_overBrightBits
+     r_mapBrightness <0.25..32.0> (default: 2) replaces r_mapOverBrightBits
   the new cvars use floating-point values (more control) and a linear scale (more intuitive)
-  new_cvar_value = pow(2, old_cvar_value), i.e. 0->1, 1->2, 2->4, 3->8, 4->16
+  to convert the old engine values to the new values:
+  r_brightness    = pow(2, r_overBrightBits)
+  r_mapBrightness = pow(2, clamp(r_mapOverBrightBits - r_overBrightBits, 0, 2))
 
 chg: r_mode selects the video mode
   r_mode 0 (default) = no screen mode change, desktop resolution
diff --git a/code/renderer/tr_bsp.cpp b/code/renderer/tr_bsp.cpp
index e9ab738..751fd7e 100644
--- a/code/renderer/tr_bsp.cpp
+++ b/code/renderer/tr_bsp.cpp
@@ -33,8 +33,7 @@ static byte* fileBase;
 
 static void R_ColorShiftLightingBytes( const byte in[4], byte out[4] )
 {
-	const float brightness = Com_Clamp( 0.25f, 32.0f, r_mapBrightness->value - r_brightness->value );
-	const int scale16 = (int)( brightness * 65536.0f );
+	const int scale16 = (int)( r_mapBrightness->value * 65536.0f );
 
 	// scale based on brightness
 	int r = ( (int)in[0] * scale16 ) >> 16;
diff --git a/code/renderer/tr_help.h b/code/renderer/tr_help.h
index bc4d948..1a5c642 100644
--- a/code/renderer/tr_help.h
+++ b/code/renderer/tr_help.h
@@ -14,10 +14,6 @@
 "allows image downscaling before texture upload\n" \
 "The maximum scale ratio is 2 on both the horizontal and vertical axis."
 
-#define help_r_mapBrightness \
-"brightness of lightmap textures\n" \
-"The lightmaps' brightness will be: r_mapBrightness - r_brightness."
-
 #define help_r_mode \
 "video mode to use when r_fullscreen is 1\n" \
 "    0 = no video mode change, desktop resolution\n" \
diff --git a/code/renderer/tr_init.cpp b/code/renderer/tr_init.cpp
index c2d6dfe..aced339 100644
--- a/code/renderer/tr_init.cpp
+++ b/code/renderer/tr_init.cpp
@@ -538,9 +538,9 @@ static const cvarTableItem_t r_cvars[] =
 	{ &r_blitMode, "r_blitMode", "0", CVAR_ARCHIVE, CVART_INTEGER, "0", XSTRING(BLITMODE_MAX), help_r_blitMode },
 	{ &r_brightness, "r_brightness", "2", CVAR_ARCHIVE | CVAR_LATCH, CVART_FLOAT, "0.25", "32", "overall brightness" },
 	// should be called r_lightmapBrightness
-	{ &r_mapBrightness, "r_mapBrightness", "4", CVAR_ARCHIVE | CVAR_LATCH, CVART_FLOAT, "0.25", "32", help_r_mapBrightness },
+	{ &r_mapBrightness, "r_mapBrightness", "2", CVAR_ARCHIVE | CVAR_LATCH, CVART_FLOAT, "0.25", "32", "brightness of lightmap textures" },
 	// should be called r_textureBrightness
-	{ &r_intensity, "r_intensity", "1", CVAR_ARCHIVE | CVAR_LATCH, CVART_FLOAT, "1", NULL, "brightness of non-lightmap textures" },
+	{ &r_intensity, "r_intensity", "1", CVAR_ARCHIVE | CVAR_LATCH, CVART_FLOAT, "1", NULL, "brightness of non-lightmap map textures" },
 	{ &r_fullscreen, "r_fullscreen", "1", CVAR_ARCHIVE | CVAR_LATCH, CVART_BOOL, NULL, NULL, "full-screen mode" },
 	{ &r_width, "r_width", "1280", CVAR_ARCHIVE | CVAR_LATCH, CVART_INTEGER, "320", "65535", "custom window/render width" help_r_mode01 },
 	{ &r_height, "r_height", "720", CVAR_ARCHIVE | CVAR_LATCH, CVART_INTEGER, "240", "65535", "custom window/render height" help_r_mode01 },