diff --git a/OSBindings/Mac/Clock Signal/Base.lproj/MachineDocument.xib b/OSBindings/Mac/Clock Signal/Base.lproj/MachineDocument.xib
index b1eeadf5a..93bf418b9 100644
--- a/OSBindings/Mac/Clock Signal/Base.lproj/MachineDocument.xib	
+++ b/OSBindings/Mac/Clock Signal/Base.lproj/MachineDocument.xib	
@@ -27,7 +27,7 @@
                 <rect key="frame" x="0.0" y="0.0" width="600" height="450"/>
                 <autoresizingMask key="autoresizingMask"/>
                 <subviews>
-                    <openGLView hidden="YES" wantsLayer="YES" useAuxiliaryDepthBufferStencil="NO" allowOffline="YES" wantsBestResolutionOpenGLSurface="YES" translatesAutoresizingMaskIntoConstraints="NO" id="DEG-fq-cjd" customClass="CSScanTargetView">
+                    <openGLView hidden="YES" wantsLayer="YES" stencilSize="8bit" useAuxiliaryDepthBufferStencil="NO" allowOffline="YES" wantsBestResolutionOpenGLSurface="YES" translatesAutoresizingMaskIntoConstraints="NO" id="DEG-fq-cjd" customClass="CSScanTargetView">
                         <rect key="frame" x="0.0" y="0.0" width="600" height="450"/>
                     </openGLView>
                     <box hidden="YES" boxType="custom" cornerRadius="4" title="Box" titlePosition="noTitle" translatesAutoresizingMaskIntoConstraints="NO" id="4ap-Gi-2AO">
diff --git a/OSBindings/Mac/Clock Signal/ScanTarget/CSScanTarget.mm b/OSBindings/Mac/Clock Signal/ScanTarget/CSScanTarget.mm
index b85da72f1..a5059fa4d 100644
--- a/OSBindings/Mac/Clock Signal/ScanTarget/CSScanTarget.mm	
+++ b/OSBindings/Mac/Clock Signal/ScanTarget/CSScanTarget.mm	
@@ -112,7 +112,7 @@ using BufferingScanTarget = Outputs::Display::BufferingScanTarget;
 	//
 	uniforms()->scale[0] = modals.output_scale.x;
 	uniforms()->scale[1] = modals.output_scale.y;
-	uniforms()->lineWidth = 1.0f / modals.expected_vertical_lines;
+	uniforms()->lineWidth = 0.75f / modals.expected_vertical_lines;	// TODO: return to 1.0 (or slightly more), once happy.
 
 	const auto toRGB = to_rgb_matrix(modals.composite_colour_space);
 	uniforms()->toRGB = simd::float3x3(
@@ -205,6 +205,11 @@ using BufferingScanTarget = Outputs::Display::BufferingScanTarget;
 		break;
 	}
 
+	// Enable blending.
+	pipelineDescriptor.colorAttachments[0].blendingEnabled = YES;
+	pipelineDescriptor.colorAttachments[0].sourceRGBBlendFactor = MTLBlendFactorSourceAlpha;
+	pipelineDescriptor.colorAttachments[0].destinationRGBBlendFactor = MTLBlendFactorOneMinusSourceAlpha;
+
 	_scanPipeline = [view.device newRenderPipelineStateWithDescriptor:pipelineDescriptor error:nil];
 }
 
@@ -219,9 +224,15 @@ using BufferingScanTarget = Outputs::Display::BufferingScanTarget;
 		[self setModals:*newModals view:view];
 	}
 
+	// Buy into framebuffer preservation.
+	// TODO: do I really need to do this on every draw?
+	MTLRenderPassDescriptor *const descriptor = view.currentRenderPassDescriptor;
+	descriptor.colorAttachments[0].loadAction = MTLLoadActionLoad;
+	descriptor.colorAttachments[0].storeAction = MTLStoreActionStore;
+	descriptor.colorAttachments[0].clearColor = MTLClearColorMake(1.0, 1.0, 0.0, 1.0);
+
 	// Generate a command encoder for the view.
 	id <MTLCommandBuffer> commandBuffer = [_commandQueue commandBuffer];
-	MTLRenderPassDescriptor *const descriptor = view.currentRenderPassDescriptor;
 	id <MTLRenderCommandEncoder> encoder = [commandBuffer renderCommandEncoderWithDescriptor:descriptor];
 
 	// Drawing. Just scans.
diff --git a/OSBindings/Mac/Clock Signal/ScanTarget/ScanTarget.metal b/OSBindings/Mac/Clock Signal/ScanTarget/ScanTarget.metal
index d5bfa4877..944222e87 100644
--- a/OSBindings/Mac/Clock Signal/ScanTarget/ScanTarget.metal	
+++ b/OSBindings/Mac/Clock Signal/ScanTarget/ScanTarget.metal	
@@ -171,9 +171,10 @@ float3 convertRed1Green1Blue1(SourceInterpolator vert, texture2d<ushort> texture
 	return float3(sample&4, sample&2, sample&1);
 }
 
+// TODO: don't hard code the 0.64 in sample##name.
 #define DeclareShaders(name, pixelType)	\
 	fragment float4 sample##name(SourceInterpolator vert [[stage_in]], texture2d<pixelType> texture [[texture(0)]]) {	\
-		return float4(convert##name(vert, texture), 1.0);	\
+		return float4(convert##name(vert, texture), 0.64);	\
 	}	\
 	\
 	fragment float4 svideoSample##name(SourceInterpolator vert [[stage_in]], texture2d<pixelType> texture [[texture(0)]], constant Uniforms &uniforms [[buffer(0)]]) {	\