Provided that heat from the bulb was under complete control, and you could place an HID 1 foot from the canopy providing well over 15,000 lumens, is it possible to have too much light? Or would the light intensity only give benefits, i.e. faster growth, denser buds, larger yields, etc.?
It is possible to burn your plants, and by burning I don't mean from heat, but from too much light. However, you would need a whole lot of light to do that. If you're using one HID light you'll be fine. Even if you're talking 1 1000w light a foot away from one plant. What I can say is this, if you can indeed keep the temp down, and you put 15,000 lumens at your canopy all you'll see is some fat ladies. I had a grow bookmarked from a professional medical-MJ grower that only grew 2 plants at a time and claimed to be pulling a pound a plant. He was using a 1000w HPS in about a 4x4 space in hydro. He had a water cooled light, a water chiller for the reservoir, and his room was air controlled so it stayed cool. He had cola's as wide as your thighs. The point is unless you're trying to give one plant 5000 watts or something silly you're not going to give them too much light. If you can control your temps, the more light the better, but there is eventually a point of diminishing returns. I would say you wouldn't want to go over 20k lumens at your canopy. Without doing the math, I would think at that much light it would just be a waste of electricity (assuming the square footage is correct).
iirc, light bleaching might become a problem as the light exceeds 10,000 lumens per square foot. I think that's what I've read.
^Agree with both -- you can have light bleaching but you almost have to try on purpose to make it happen. FYI I run a 250w MH/HPS (each rated over 20,000 lumens) within about a foot of the plant tops, and sometimes closer, with no problems.