you also need to understand that 1KW/sqm of sun light hits the earths surface but you will never have a 1KW/sqm light, oh you might think that your light is bright but it is not, our eyes are phenomenal light detectors with a far superior range than any man made sensor, our eyes adjust automatically so what you think is bright is not really bright at all and infact nothing compared to the sun, think 1KW/sqm and then think how many watts/sqm your average 100W bulb is putting in an average room bearing in mind that your looking at a source of 2-3 watts in reality as the rest goes in heat.