What is a good range for light lumens intensity. I am measuring about 500 lumens at plant height. Using 500 watt full spectrum LED.
500 lumens seems really low and according to Google a 5-7 watt led makes 500 lumens which sounds like more Chinese false advertising if your light manufacturer claims 500 watts the reality most likely is 5-7 watts. Can you provide more info on your light like a pic of the nameplate with electrical info. Some really smart people will respond to your post soon.
Welcome to the forum.
Depends on light source and how measuring device is calibrated.
If you have an iPhone, check out the app Photone. It gives par readings correctly (within a tolerance of 10-20 +/-) on iPhone, but on Android it is way off( within a tolerance of 150-175 +/-).