Garyh, I dont know the reason of there were hundreds of lightmeters are sold at surveying sites here. And why they advertise them as 20000 lux. May be architects, surveyors shoot digital pictures of the works and needed a real lightmeter, I have no idea. They are cheap , big and complicated and I did not see one except internet.Not sure what you have come across referring to a digital lightmeter for surveying? Or how something that is good and proper for surveying might be just as useful for photography.
Its 8 AM , Still surfing and I dont know how these sleepless nights ends .