There are two main things to consider when it comes to light intensity for cannabis plants. The first is the stage of growth your plant is in. Seedlings and young plants need less intense light, while flowering plants need much more. The second is the type of light you're using. LEDs and other modern grow lights can usually handle higher intensities than traditional HID lights.
To figure out exactly how much light your plant needs, you'll want to measure the light intensity in your grow space. You can get a light meter specifically designed for plants to do this.