diff --git a/platformio.ini b/platformio.ini
index 8499eb2..c87cdc1 100644
--- a/platformio.ini
+++ b/platformio.ini
@@ -38,6 +38,7 @@ build_flags =
     -D dataTCS34725_lux_minchange=500
     -D dataTCS34725_lux_senddelaymax=1000*60*1
     -D dataTCS34725_colortemp_minchange=100
+    -D TCS34725_LUXFACTOR=0.3 #measured with luxmeter. with half tennis ball was 1.7ev less. 1/2^1.7=0,3078
 
     -D SENSOR_HS1101
     -D HS1101PIN=D5
diff --git a/src/main.cpp b/src/main.cpp
index f097a33..c2ad2a4 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -188,6 +188,9 @@ struct sensordata
   uint16_t value_colortemp, value_tcs_lux, value_tcs_r,value_tcs_g,value_tcs_b,value_tcs_c;
   unsigned long lastread_tcs34725=0;
   #define TCS34725_MINLUXFORCT 30 //send only colortemperature values if lux is at least this high
+  #ifndef TCS34725_LUXFACTOR
+    #define TCS34725_LUXFACTOR 1
+  #endif
 #endif
 
 #ifdef SENSOR_ANEMOMETER
@@ -892,7 +895,7 @@ void loop_TCS34725_lux()
       }
     }
     //value_tcs_lux = tcs.calculateLux(value_tcs_r, value_tcs_g, value_tcs_b);
-    value_tcs_lux = tcs.lux;
+    value_tcs_lux = tcs.lux*TCS34725_LUXFACTOR;
 
     if (abs((int)d.lastsentvalue-value_tcs_lux)>=d.minchange){  //int abs
       _changed=true;