"Light penetration" refers to the ability of light to pass through a material or substance. It is a measure of how easily or deeply light can travel through something. Full definition
There is lots of light penetration from above and several escape routes. (Dive-The-World.com)
They can be made of thick fabric so you can have less light penetration in your room or a thin material so the light can penetrate a little more. (thefashionablehousewife.com)
We're sure you'll experience sparkling clear water, better light penetration and enhanced growth of corals, fish, and aquatic plants. (bluelifeusa.com)