Unless I'm running vertical lighting I'll partially defoliate the lower 1/3 of my plants since not much light is going to get through a dense canopy anyway. Those canopy fan leaves are like little solar panels but they will block light. What light does get through will be a result of canopy movement and at lower intensities as a result of the distance from the light.
When flowering at the tops I like to see a broad spectrum lamp (I get this with an 18" lamp-canopy separation) emitting 600-700 uMoles over my 13 hour lights on cycles. This gives me between 28-33 Moles/Day which from my experiences with Indica dominants has been ideal. If I have multiple lights and put the lamp-canopy distance @ 12-14" that same 13 hours will put me in the 40 Moles/Day region for Sativa dominants. There's a Moles/Day chart on page 17 of the link I gave you that will make this easier to understand.
On a 4 ft plant with good canopy movement I aim to get an average of 200-300 uMoles at the lower flowering sites but unlike the canopy where light is a constant intensity this is going to be an irregular reading unless you LST. If I've got multiple plants running taller than 5 ft I'll run the vertical VPAR light, no defoliation and pick up the lower branches that way.
