   Serial.print("Shutter detected: 1/");
   Serial.print(shutter);
   Serial.print("s (");
-  Serial.print(duration);
-  Serial.print("µs)");
+  Serial.print(duration / 1000);
+  Serial.print("ms)");
 
   Serial.print("    Avg (");
   Serial.print(count);
   Serial.print(") 1/");
   Serial.print(avgShutter);
   Serial.print("s (");
-  Serial.print(mean);
-  Serial.print("µs) σ:");
-  Serial.println(stdDevSample);
+  Serial.print(mean / 1000 );
+  Serial.print("ms) σ:");
+  Serial.println(stdDevSample / 1000);
 }
 
 void debugRawValues()

        calcStats(endTime - startTime);
      }
    }
  }
}

Requires a light source at one end of the camera and a photoresistor / LDR
on the other end.



          +5V
           |
  \        |
   \|   -------
\  -\  /    |  \
 \|   /     |   \
 -\  /      |    \
     |    |/     |
     |    |      |   phototransistor
     |    |\     |
     \      |    /
      \     |   /
       \    |  /
        -------
           |
           |
           +-------- Analog pin 0
           |
          <|  -/
           |> /|
          <| /
           |>
          </         potentiometer
          /|>
         /<|
        /  |>
           |
           |
         -----       ground
          ---


Also requires a potentiometer to set the light threshold value:
+5V ----------/\/\/\/----------- ground
