diff --git a/build-number.txt b/build-number.txt
index 2681747..1b1c131 100644
--- a/build-number.txt
+++ b/build-number.txt
@@ -1 +1 @@
-277
+280
diff --git a/src/light_sensor.c b/src/light_sensor.c
index e12a355..3f1c9af 100644
--- a/src/light_sensor.c
+++ b/src/light_sensor.c
@@ -66,7 +66,7 @@ void LightSensor_Poll(void)
     {
         unsigned int measurement = LightSensor_Measurement;
         LightSensor_NewMeasurement = false;
-        float brightness = 1.0f - measurement / 65535.0f;
+        float brightness = 65535.0f / measurement;
         LightSensor_AbsoluteBrightness = LIGHTSENSOR_LAMBDA * LightSensor_AbsoluteBrightness
             + (1.0f - LIGHTSENSOR_LAMBDA) * brightness;