The reason I ask is because I have some plants indoors under some shop lights in a spare bedroom, but recently bought a 400 W HPS which will be much brigher.

Is there some point where lights are too bright? even when temperatures stay around 75 degrees?

So I guess I have too questions:

(1) where can I find a comprehensive reference that describes plant light requirements in terms of lumens / foot candles and

(2) Is there such a thing as too much light "burning" or otherwise damaging plants at regular indoor temperatures?

I'm mostly propagating plants under the lights, the plants I have inside now are hibiscus, hydrangea, and wisteria cuttings, but will start some acer seeds soon.

Deep shade plants, typical good houseplants that don't need a bright window, will do well in 100 foot-candles or less. Usually they will burn in bright light.

Regular shade plants would be more like 200-500 foot-candles. Many houseplants will be in this category. They will take over 1,000 foot-candles for short periods but will be damaged if they get it for too long.

Part sun plants will be around 1,000-1,500 foot-candles. They can take full sun intensity of perhaps 10,000 foot-candles for short periods.

Full sun plants prefer a few thousand foot-candles. Most of them will take full sun intensity of 10,000-15,000 foot-candles for several hours without a problem. The problems will come from heating. Just make sure you have air movement over the plants.

Remember that the intensity that a plant can experience naturally would not be sustained for 14 hours, so don't necessarily expect to be able to put even a full sun plant in 10,000 foot-candles for 14 hours every day. Full sun is around 10,000 foot-candles, open shade on a sunny day is around 1,000 foot-candles, deep shade may be as low as 100 foot-candles. Indoors, normal home lighting will be 10-50 foot-candles, perhaps as much as 100 foot-candles in work areas such as a kitchen counter or lit sewing table.

Here are a couple charts I found doing a google search for "plants footcandles".

http://hgic.clemson.edu/factsheets/HGIC1450.htm

http://www.greenworks.com/plants.htm

It will likely be harder to find statistics for outdoor plants. I can tell you from experience that the hibiscus cuttings will root well under shop lights (even better if you put a humidity dome over them and use just the lights, no window), and with gradual acclimation, you can't burn a hibiscus on a 400W light.

I would guess that hydrangea would be much more sensitive.