diff --git a/source/common/gamecvars.cpp b/source/common/gamecvars.cpp
index e6eecd6b5..ddfeed8a0 100644
--- a/source/common/gamecvars.cpp
+++ b/source/common/gamecvars.cpp
@@ -476,30 +476,25 @@ CUSTOM_CVAR(String, playername, "Player", CVAR_ARCHIVE | CVAR_USERINFO)
 CUSTOM_CVARD(Float, vid_gamma, 1.f, CVAR_ARCHIVE | CVAR_GLOBALCONFIG, "adjusts gamma component of gamma ramp")
 {
 	if (self < 0) self = 0;
-	else if (self > 5) self = 5;
-	// todo: tell the system to update
+	else if (self > 4) self = 4;
 }
 
 CUSTOM_CVARD(Float, vid_contrast, 1.f, CVAR_ARCHIVE | CVAR_GLOBALCONFIG, "adjusts contrast component of gamma ramp")
 {
 	if (self < 0) self = 0;
 	else if (self > 5) self = 5;
-	// todo: tell the system to update
 }
 
 CUSTOM_CVARD(Float, vid_brightness, 0.f, CVAR_ARCHIVE | CVAR_GLOBALCONFIG, "adjusts brightness component of gamma ramp")
 {
-	if (self < 0) self = 0;
-	else if (self > 5) self = 5;
-	// todo: tell the system to update
+	if (self < -2) self = -2;
+	else if (self > 2) self = 2;
 }
 
-
-CUSTOM_CVARD(Float, vid_saturation, 0.f, CVAR_ARCHIVE | CVAR_GLOBALCONFIG, "adjusts saturation component of gamma ramp")
+CUSTOM_CVARD(Float, vid_saturation, 1.f, CVAR_ARCHIVE | CVAR_GLOBALCONFIG, "adjusts saturation component of gamma ramp")
 {
 	if (self < -3) self = -3;
 	else if (self > 3) self = 3;
-	// todo: tell the system to update
 }
 
 CVAR(Int, gl_satformula, 1, CVAR_ARCHIVE|CVAR_GLOBALCONFIG);
diff --git a/source/common/rendering/gl/renderer/gl_postprocess.cpp b/source/common/rendering/gl/renderer/gl_postprocess.cpp
index c835aa0ac..3160dfb92 100644
--- a/source/common/rendering/gl/renderer/gl_postprocess.cpp
+++ b/source/common/rendering/gl/renderer/gl_postprocess.cpp
@@ -59,13 +59,13 @@ void FGLRenderer::RenderScreenQuad()
 #else
 	glBegin(GL_TRIANGLE_STRIP);
     glVertexAttrib2f(1, 0, 0);
-	glVertex2f(-1, -1);
+	glVertexAttrib2f(0, -1, -1);
     glVertexAttrib2f(1, 0, 1);
-	glVertex2f(-1, 1);
+	glVertexAttrib2f(0, -1, 1);
     glVertexAttrib2f(1, 1, 0);
-	glVertex2f(1, -1);
+	glVertexAttrib2f(0, 1, -1);
     glVertexAttrib2f(1, 1, 1);
-	glVertex2f(1,1);
+	glVertexAttrib2f(0, 1,1);
 	glEnd();
 #endif
 }