ours is an 8 ft like these here and the fabrick is like a fine mesh so it lets the light through. You do have to move it slightly (couple of inches) every few days so that the grass under the feet isn't killed.
Gobbledigook - woulod say you need to try them out (lots of places let you - it's a great day out!). We went foe a 14' Supertramp as more tightly sprung than TP so takes more weight & supposedly lasts longer.
Also - agree that the grass grows better under it, and is very easy to rotate so legs don't kill the same bit of grass.