diff --git a/gui/src/aaregui/panels/raster_data_collection.py b/gui/src/aaregui/panels/raster_data_collection.py
index c85f07dc..09a575e3 100644
--- a/gui/src/aaregui/panels/raster_data_collection.py
+++ b/gui/src/aaregui/panels/raster_data_collection.py
@@ -92,7 +92,7 @@ class RasterDataCollectionPanel(ScanSettingsPanel):
         slider = QSlider(orientation=Qt.Orientation.Horizontal, parent=self)
         slider.setRange(0, 255)
         slider.setValue(127)
-        slider.valueChanged.connect(lambda: self.raster_alpha_changed.emit(slider.value()))
+        slider.valueChanged.connect(lambda: self.raster_alpha_changed.emit(255 - slider.value()))
         self._layout.addWidget(slider, 8, 1, 1, 3)
 
         horizontal_spacer = QSpacerItem(