Calculating the lumens per square meter isn't very hard. Figuring out what is enough isn't so easy, however. If I use 8 23W CFLs (100W equivalent) in my little 14x24 shop, I get about 400 lumens/m2. That is a little less than recommended for an office (500) and well under what is recommended for a mechanical workshop (750). If I use 8 32W tubes (4 foot), I get almost 700 lumens/m2. It seems like office level lighting wouldn't really be that bad in my shop.
So just for grins, I calculated the lumens/m2 for our great room. It is a large high ceiling room with one chandeler in the center with 6 60W bulbs. I got 65 lumens/m2. Recommended normal house level is 250 lumens/m2. I've been thinking a fixture with 4 of the 32W CFLs might be enough in there but they aren't. I'm going to have to hang a couple more fixtures (joy of joys, it means working in the attic 16.5 feet off the floor below).
But back on my shop, do you guys happen to know the lumens/m2 for your setups?