You are correct Fabolusus - the book I noted goes into that extensively - Charles Marden Fitch's "Growing Orchids Under Lights".
Here is another article on lighting that has some good information -
http://www.simplyhydro.com/why_hydro.htm. It also mentions light movers with HID lighting for efficiency.
Arlene - notice the part on fluorescents - partly copied here -
"These tubes produce 68 lumens per watt, for a total of 2750 lumens. Fluorescents are ideal for initial propagation because they produce almost no reciprocal heat. You can hang a four tube fixture six to eight inches above your plant canopy, and then just keep raising it as your plants grow, without fear of burning your leaves. In this example, we will scale down the size of our test garden. Earlier, we have been using a five feet by five feet garden as a reference point. For this example, we wil use a two feet by four feet garden. A two feet by four feet fixture can hold four bulbs. This will give us a total of 11,000 lumens (4 bulbs multiplied by 2750 individual lumens = 11,000 lumens). Allowing for "spilled" light, we are probably generating about 1031.25 F.C. (11,000 lumens multiplied by 75% = 8250 lumens...8250 lumens divided by eight square feet =
1031.25 Foot Candles). This is assuming that the lights are placed DIRECTLY over your plants. As you raise your lighting, your light intensity drastically drops. When you double the distance between your light and your plants, you cut the light intensity by four times."