diff --git a/hdr/shaders/crt-sony-megatron-sdr.slangp b/hdr/shaders/crt-sony-megatron-sdr.slangp
index c0fa22c..c0e12ba 100644
--- a/hdr/shaders/crt-sony-megatron-sdr.slangp
+++ b/hdr/shaders/crt-sony-megatron-sdr.slangp
@@ -2,4 +2,3 @@
 
 hcrt_hdr = "0.000000"
 
-hcrt_gamma_in = "2.000000"
diff --git a/hdr/shaders/include/colour_grade.h b/hdr/shaders/include/colour_grade.h
index 9aa2c30..eaec5fb 100644
--- a/hdr/shaders/include/colour_grade.h
+++ b/hdr/shaders/include/colour_grade.h
@@ -73,7 +73,8 @@ vec3 WhiteBalance(float temperature, vec3 colour)
 
 float r601ToLinear_1(const float channel)
 {
-	return (channel >= 0.081f) ? pow((channel + 0.099f) * (1.0f / 1.099f), (1.0f / 0.45f)) : channel * (1.0f / 4.5f);
+	//return (channel >= 0.081f) ? pow((channel + 0.099f) * (1.0f / 1.099f), (1.0f / 0.45f)) : channel * (1.0f / 4.5f);
+	return (channel >= 0.081f) ? pow((channel + 0.099f) * (1.0f / 1.099f), HCRT_GAMMA_IN) : channel * (1.0f / 4.5f);
 }
 
 vec3 r601ToLinear(const vec3 colour)
@@ -84,7 +85,8 @@ vec3 r601ToLinear(const vec3 colour)
 
 float r709ToLinear_1(const float channel)
 {
-	return (channel >= 0.081f) ? pow((channel + 0.099f) * (1.0f / 1.099f), (1.0f / 0.45f)) : channel * (1.0f / 4.5f);
+	//return (channel >= 0.081f) ? pow((channel + 0.099f) * (1.0f / 1.099f), (1.0f / 0.45f)) : channel * (1.0f / 4.5f);
+	return (channel >= 0.081f) ? pow((channel + 0.099f) * (1.0f / 1.099f), HCRT_GAMMA_IN) : channel * (1.0f / 4.5f);
 }
 
 vec3 r709ToLinear(const vec3 colour)
@@ -173,7 +175,7 @@ vec3 ColourGrade(const vec3 colour)
 
    const vec3 white_point     = WhiteBalance(kTemperatures[colour_system] + HCRT_WHITE_TEMPERATURE, colour);
 
-   const vec3 linear          = pow(white_point, vec3(HCRT_GAMMA_IN));
+   const vec3 linear          = r601ToLinear(white_point); //pow(white_point, vec3(HCRT_GAMMA_IN));
 
    const vec3 xyz             = linear * kColourGamut[colour_system];
 
diff --git a/hdr/shaders/include/parameters.h b/hdr/shaders/include/parameters.h
index 84e8534..e0c0aa6 100644
--- a/hdr/shaders/include/parameters.h
+++ b/hdr/shaders/include/parameters.h
@@ -31,7 +31,7 @@
 #pragma parameter hcrt_brightness                    "    Brightness"                                               0.0     -1.0   1.0      0.01
 #pragma parameter hcrt_contrast                      "    Contrast"                                                 0.0     -1.0   1.0      0.01
 #pragma parameter hcrt_saturation                    "    Saturation"                                               0.0     -1.0   1.0      0.01
-#pragma parameter hcrt_gamma_in                      "    Gamma"                                                    2.4      1.0   5.0      0.01
+#pragma parameter hcrt_gamma_in                      "    Gamma"                                                    2.22     1.0   5.0      0.01
 #pragma parameter hcrt_pin_phase                     "    Pin Phase"                                                0.00    -0.2   0.2      0.01
 #pragma parameter hcrt_pin_amp                       "    Pin Amp"                                                  0.00    -0.2   0.2      0.01
 #pragma parameter hcrt_space3                        " "                                                            0.0      0.0   0.0001   0.0001