The Ring of X-Ray Vision (Dungeon Master’s Guide, pg. 193) says:
While wearing this ring, you can use an action to speak its command word. When you do so, you can see into and through solid matter for 1 minute. This vision has a radius of 30 feet. To you, solid objects within that radius appear transparent and don’t prevent light from passing through them. The vision can penetrate 1 foot of stone, 1 inch of common metal, or up to 3 feet of wood or dirt. Thicker substances block the vision, as does a thin sheet of lead.
Suppose I am a pirate. After clearing the top deck of an unfortunate cargo ship, me mateys and I head below deck where the ship’s crew have extinguished all of the lanterns to make the interior totally dark. But I have a Ring of X-ray Vision. I speak the command word.
From my perspective, does my X-ray vision cause day light from outside to pass through the upper deck into this lower deck, illuminating the space as if it were day light?