diff --git a/bin/data/presets/burn-guided.pst b/bin/data/presets/burn-guided.pst
index fdb85e76..6f0e68c0 100644
--- a/bin/data/presets/burn-guided.pst
+++ b/bin/data/presets/burn-guided.pst
@@ -20,7 +20,7 @@ connect:blend:burn:output:blend:dodge:back
 connect:blend:dodge:output:colour:01:input
 param:blend:burn:opacity:1
 param:blend:burn:mode:0
-param:blend:burn:mask:2
+param:blend:burn:mask:1
 param:exposure:burn:exposure:2
 param:draw:burn:opacity:5
 param:draw:burn:hardness:1
diff --git a/bin/data/presets/burn.pst b/bin/data/presets/burn.pst
index 44c7d65f..5e8b186f 100644
--- a/bin/data/presets/burn.pst
+++ b/bin/data/presets/burn.pst
@@ -17,5 +17,5 @@ connect:blend:burn:output:blend:dodge:back
 connect:blend:dodge:output:colour:01:input
 param:blend:burn:opacity:1
 param:blend:burn:mode:0
-param:blend:burn:mask:2
+param:blend:burn:mask:1
 param:exposure:burn:exposure:2
diff --git a/bin/data/presets/dodge-guided.pst b/bin/data/presets/dodge-guided.pst
index f34fe9d3..857a2870 100644
--- a/bin/data/presets/dodge-guided.pst
+++ b/bin/data/presets/dodge-guided.pst
@@ -20,7 +20,7 @@ connect:blend:dodge:output:blend:burn:back
 connect:blend:burn:output:colour:01:input
 param:blend:dodge:opacity:1
 param:blend:dodge:mode:0
-param:blend:dodge:mask:2
+param:blend:dodge:mask:1
 param:exposure:dodge:exposure:-2
 param:draw:dodge:opacity:5
 param:draw:dodge:hardness:1
diff --git a/bin/data/presets/dodge.pst b/bin/data/presets/dodge.pst
index 4092ef51..7d3142d3 100644
--- a/bin/data/presets/dodge.pst
+++ b/bin/data/presets/dodge.pst
@@ -17,5 +17,5 @@ connect:blend:dodge:output:blend:burn:back
 connect:blend:burn:output:colour:01:input
 param:blend:dodge:opacity:1
 param:blend:dodge:mode:0
-param:blend:dodge:mask:2
+param:blend:dodge:mask:1
 param:exposure:dodge:exposure:-2
diff --git a/src/pipe/modules/blend/main.comp b/src/pipe/modules/blend/main.comp
index 5ecb1ec1..b37b545d 100644
--- a/src/pipe/modules/blend/main.comp
+++ b/src/pipe/modules/blend/main.comp
@@ -49,12 +49,12 @@ main()
   if(params.mask == 1)
   {
     float mask = texture(img_mask, tc).r;
-    t = clamp(params.opacity*(1.0-mask), 0, 1);
+    t = clamp(params.opacity*mask, 0, 1);
   }
   else if(params.mask == 2)
   {
     float mask = texture(img_mask, tc).r;
-    t = clamp(params.opacity*mask, 0, 1);
+    t = clamp(params.opacity*(1.0-mask), 0, 1);
   }
 
   if(params.mode == 0)
diff --git a/src/pipe/modules/shared/guided2f.comp b/src/pipe/modules/shared/guided2f.comp
index 66c6d2d9..6d5071f8 100644
--- a/src/pipe/modules/shared/guided2f.comp
+++ b/src/pipe/modules/shared/guided2f.comp
@@ -34,8 +34,8 @@ main()
   const float var = mean_corr.z - mean_corr.x * mean_corr.x;
   const float cov = mean_corr.w - mean_corr.x * mean_corr.y;
   // XXX what's the valid range here?
-  // const float a = clamp(cov / (var + 100*cov*params.epsilon), 0.0f, 1.0f);
-  const float a = clamp(cov / (var + 1e-8 + params.epsilon*params.epsilon), -1e5, 1e5); // some safety margin to avoid infty etc
+  const float a = clamp(cov / (var + 1e-8 + params.epsilon*params.epsilon), -5.0f, 5.0f);
+  // const float a = clamp(cov / (var + 1e-8 + params.epsilon*params.epsilon), -1e5, 1e5); // some safety margin to avoid infty etc
   // const float a = cov / (var + params.epsilon*params.epsilon);
   const float b = mean_corr.y - a * mean_corr.x;
   imageStore(img_out, ipos, vec4(a, b, 0.0, 0.0));