diff --git a/src/widgets/aperture_priority_page.py b/src/widgets/aperture_priority_page.py
index 7ad3e2a..b3d7699 100644
--- a/src/widgets/aperture_priority_page.py
+++ b/src/widgets/aperture_priority_page.py
@@ -43,13 +43,23 @@ class AperturePriorityPage(Gtk.Box):
     aperture_priority_aperture_dropdown = Gtk.Template.Child()
     aperture_priority_time_label = Gtk.Template.Child()
 
-    def onValuesChanged(self, isoSpeed: int,  sensorValue: float, sensorUnit: str):
+    lastSensorValue = None
+
+    def onValuesChanged(self, isoSpeed: int, sensorValue: float, sensorUnit: str):
         # Check the unit is absolute ("lux")
         if sensorUnit != "lux":
             return
 
+        self.lastSensorValue = sensorValue
+        self.updateView(isoSpeed, sensorValue)
+
+
+    def onIsoSpeedChanged(self, isoSpeed: int):
+        if self.lastSensorValue:
+            self.updateView(isoSpeed, self.lastSensorValue)
+
+    def updateView(self, isoSpeed: int, sensorValue: float):
         apertureValue = self.aperture_priority_speed_dropdown_values[self.aperture_priority_aperture_dropdown.get_selected()]
         shutterSpeed = EVCalculator.calcShutterSpeed(isoSpeed, sensorValue, apertureValue)
         # TODO: Round shutter speed value to nearest existing value and set label color to red if outside 1 stop range
         self.aperture_priority_time_label.set_label("f/ {:.2f}".format(shutterSpeed))
-
diff --git a/src/widgets/manual_exposure_page.py b/src/widgets/manual_exposure_page.py
index c3cbdcd..ab7152c 100644
--- a/src/widgets/manual_exposure_page.py
+++ b/src/widgets/manual_exposure_page.py
@@ -30,3 +30,5 @@ class ManualExposurePage(Gtk.Box):
         if sensorUnit != "lux":
             return
 
+    def onIsoSpeedChanged(self, isoSpeed: int):
+        print("ME: onIsoSpeedChanged {}".format(isoSpeed))
diff --git a/src/widgets/sensor_readings_page.py b/src/widgets/sensor_readings_page.py
index 4b8dd47..33b1aff 100644
--- a/src/widgets/sensor_readings_page.py
+++ b/src/widgets/sensor_readings_page.py
@@ -44,3 +44,5 @@ class SensorReadingsPage(Gtk.Box):
         if self.ev_label:
             self.ev_label.set_label("{:.1f} EV".format(ev))
 
+    def onIsoSpeedChanged(self, isoSpeed: int):
+        print("SR: onIsoSpeedChanged {}".format(isoSpeed))
diff --git a/src/widgets/time_priority_page.py b/src/widgets/time_priority_page.py
index e32144a..b651c36 100644
--- a/src/widgets/time_priority_page.py
+++ b/src/widgets/time_priority_page.py
@@ -51,13 +51,22 @@ class TimePriorityPage(Gtk.Box):
     time_priority_speed_dropdown = Gtk.Template.Child()
     time_priority_aperture_label = Gtk.Template.Child()
 
+    lastSensorValue = None
+
     def onValuesChanged(self, isoSpeed: int, sensorValue: float, sensorUnit: str):
         # Check the unit is absolute ("lux")
         if sensorUnit != "lux":
             return
 
+        self.lastSensorValue = sensorValue
+        self.updateView(isoSpeed, sensorValue)
+
+    def onIsoSpeedChanged(self, isoSpeed: int):
+        if self.lastSensorValue:
+            self.updateView(isoSpeed, self.lastSensorValue)
+
+    def updateView(self, isoSpeed: int, sensorValue: float):
         shutterSpeed = self.time_priority_speed_dropdown_values[self.time_priority_speed_dropdown.get_selected()]
         apertureValue = EVCalculator.calcAperture(isoSpeed, sensorValue, shutterSpeed)
         # TODO: Round aperture value to nearest existing value and set label color to red if outside 1 stop range
         self.time_priority_aperture_label.set_label("f/ {:.2f}".format(apertureValue))
-
diff --git a/src/window.py b/src/window.py
index c147af1..acb3ca6 100644
--- a/src/window.py
+++ b/src/window.py
@@ -89,4 +89,16 @@ class LumosWindow(Adw.ApplicationWindow):
         dialog.add_response("close", "Close")
         dialog.choose(self, None, None)
 
+    @Gtk.Template.Callback()
+    def onIsoSpeedChanged(self, dropDown: Gtk.DropDown, _: any) -> None:
+        # Changed ISO value, notify all pages
+        isoSpeed = int(dropDown.get_selected_item().get_string()[4:])
+        if self.aperture_priority_page_widget:
+            self.aperture_priority_page_widget.onIsoSpeedChanged(isoSpeed)
+        if self.time_priority_page_widget:
+            self.time_priority_page_widget.onIsoSpeedChanged(isoSpeed)
+        if self.manual_page_widget:
+            self.manual_page_widget.onIsoSpeedChanged(isoSpeed)
+        if self.sensor_readings_page_widget:
+            self.sensor_readings_page_widget.onIsoSpeedChanged(isoSpeed)
 
diff --git a/src/window.ui b/src/window.ui
index 6c7fca5..571b696 100644
--- a/src/window.ui
+++ b/src/window.ui
@@ -27,6 +27,7 @@
                   </object>
                 </property>
                 <property name="selected">1</property> <!-- ISO 100 -->
+                <signal name="notify::selected-item" handler="onIsoSpeedChanged"/>
               </object>
             </child>
             <child type="end">
@@ -48,7 +49,7 @@
               <object class="AdwBanner" id="error_banner">
                 <property name="title" translatable="true">Unable to access light sensor</property>
                 <property name="button-label" translatable="true">Details</property>
-                <signal name="button-clicked" handler="showErrorDetails"/>"
+                <signal name="button-clicked" handler="showErrorDetails"/>
               </object>
             </child>
             <child>