Do Doors and trapdoors block light?

Will a door or a trapdoor diminish or block out a light source on the other side of it? If so, by how much, and does the direction in which the door is placed change this effect?

Solution 1:

No, doors and trapdoors act just like empty space.

• The only substance which reduces “block” light (light cast by torches, etc) but does not entirely stop it is water; light level reduces by 3 rather than the normal 1 for each block of water or ice it passes through. (Despite what Minecraft Wiki currently says in one section, pistons have no effect, and slabs and stairs stop light propagation completely, though they themselves may be drawn lit. I have also specifically confirmed that doors do not stop or reduce light.)

• Water, ice, and leaves also stop sunlight rays, converting them to 'block light' at that point (thus these blocks will cast a shadow on the ground whereas other transparent blocks will not).

(Source: Direct experiments in Minecraft 1.4.6. I built a tunnel with a torch at one end, then placed various blocks between me and the torch while watching for changes in the bl debug screen field.)

If you want a door which stops light, you must use pistons pushing opaque blocks to function as a door.