That ratio is defined by the light set that you are using. First what kinf of lights are you using...LED, LEC, HPS, ....you photo doesn´t give infomations about that. Normally according to a full spectrum LED of 150 watts (in my case i use two TS1000 Mars Hydro, so 150 watts each....so i have a full LED full spectrum set of 300 watts covering 0,65 m2 (normalyy 80 X80 area) and the height is 180 cm, so from the plants canopy to the light panels the reference is 30 cms distance from the LED panel to the plant canopy. You should have zigzag hangers that allow you to put the distance that you should use, both for a perfect coverage and to avoid light burning. So tell me more about the kind of lights that you are using, the watts that they emanate, if it is a full spectrum light system, etç...otherwise this question is very difficult to reply