const int led = 4;

void setup() {
  Serial.begin( 9600 );
  pinMode( led, OUTPUT );
}

void loop() {
  int foto = analogRead(A6);

  int conversion = 780 - foto;

  if( conversion < 0 ){
    conversion *= -1;
  }
    
  Serial.print( "Foto: " );
  Serial.print( foto );
  Serial.println( "" );

  Serial.print( "Conv: " );
  Serial.print( conversion );
  Serial.println( "" );

  analogWrite( led, conversion );
  delay( 1000 );
  
}