a bit more complex, the relationship is only linear to an extent

More light = more photosynthesis; until a point at which it levels off at its max rate despite additional light

Too much light can cause bleaching, and too much light is most harmful to seedlings, clones, or plabts in very cold temps... but you have to have much more than 400 watts to bleach a plant I think

The general rule for folks like us is the more light the better!