Good question. So what I found works best is to keep light at the height it's at until the tallest plant's leaves begins to turn away from the light.
Then you can either turn down the intensity, raise your light or begin some training on your plants to lower they're canopy.
Either one of these will help you grow an even canopy but what helps the most is how you train your plants. Topping, mainline, HST, LST, scrog etc.
Hope this helps