"Franz Heymann"
snip
How many lumens per square metre do I need for overwintering rooted
cuttings of typical hardy plants?
How many lumens per square metre does the lamp provide at specific
distances?
Franz

Hi Franz
Here are some technical sites for you. i don't know if they will help as I don't
understand a word of the content :~)

http://www.littlegreenhouse.com/guide3.shtml
http://homeharvest.com/growlightglossary.htm
http://www.growell.co.uk/g/4/The_GroWell_GroW_Tent.html
http://generalhorticulture.tamu.edu/...ght/light.html
http://www.specialty-lights.com/plan...questions.html
http://www.shroomery.org/index/par/23844

Plus loads more via google with light lumen indoor plant as search
words..........
jenny