diff --git a/greenpithumb/light_sensor.py b/greenpithumb/light_sensor.py
index 4366da8..4800c94 100644
--- a/greenpithumb/light_sensor.py
+++ b/greenpithumb/light_sensor.py
@@ -4,6 +4,14 @@
 _LIGHT_SENSOR_MAX_VALUE = adc.PIN_MAX_VALUE
 
 
+class Error(Exception):
+    pass
+
+
+class LightSensorLowError(Error):
+    pass
+
+
 class LightSensor(object):
     """Wrapper for light sensor."""
 
@@ -21,7 +29,10 @@ def get_light_level(self):
         light_level = self._adc.read_pin(adc.PIN_LIGHT_SENSOR)
 
         if light_level < _LIGHT_SENSOR_MIN_VALUE:
-            raise ValueError('Light sensor reading out of range')
+            raise LightSensorLowError(
+                ('Light sensor reading of %.1f is less than the minimum '
+                 'expected value of %.1f.') % (light_level,
+                                               _LIGHT_SENSOR_MIN_VALUE))
 
         light_level_as_pct = 100 * (
             (light_level - _LIGHT_SENSOR_MIN_VALUE) /
diff --git a/tests/test_light_sensor.py b/tests/test_light_sensor.py
index 13fd71e..f6d0f66 100644
--- a/tests/test_light_sensor.py
+++ b/tests/test_light_sensor.py
@@ -23,7 +23,7 @@ def test_light_50_pct(self):
 
     def test_light_level_too_low(self):
         """Light sensor value less than min should raise a ValueError."""
-        with self.assertRaises(ValueError):
+        with self.assertRaises(light_sensor.LightSensorLowError):
             self.mock_adc.read_pin.return_value = (
                 light_sensor._LIGHT_SENSOR_MIN_VALUE - 1)
             self.light_sensor.get_light_level()