“Light your wands, can’t you? And hurry, we have little time!”
-- Griphook the Goblin in the Lestrange Gringotts Vault (DH26)
The Wand-Lighting Charm causes a small beam of light to shine from the end of the caster’s wand. The light is a directed beam rather than a general light source.
References from the canon
- This spell is used frequently as people skulk about the castle or the Forbidden Forest. Harry uses it when he, Ron and Fang follow the spiders to Aragog (CS15), and later as they proceed with Lockhart into the Chamber of Secrets (CS16).
- Harry used the spell on Magnolia Crescent when he thought he spied The Grim while waiting for the Knight Bus (PA3). He also used "Lumos" to navigate the twisting tunnel from Hogwarts to Honeydukes (PA10). Ron illuminates the Whomping Willow when Crookshanks opened the tunnel (PA13), and so does Harry as the Willow pummels him with branches on the way to the Shrieking Shack (PA17).
- Dumbledore even used one when looking for Mr. Crouch (GF28), and his beam of light was just as narrow and flashlight-like as Harry's usually is. You'd think Dumbledore would have been able to summon up something a little brighter.
- When Harry lost his wand during the Dementor attack, he desperately said Lumos and to his surprise, the tip of his wand lit up even though he wasn't holding the wand at the time. The light from a Lumos spell works even when the Dementors' presence had cancelled out the light from the streetlamps and even the stars (OP1)
- The spell to turn the light off is the Wand-Extinguishing Charm (Nox).
- Cast by Harry while searching both number twelve, Grimmauld Place (DH10) and while searching the Lestranges' vault (DH26).
"lumen" L. light
Despite what we see in the films, there is no evidence in canon for stronger levels of the Lumos spell (e.g. Lumos Maxima). In fact, if such a stronger version of the spell existed, Dumbledore would certainly have used it while searching the forest for Barty Crouch Sr. Instead, he uses the same relatively weak, narrow beam Lumos that we see elsewhere in the books:
"They were here," Harry said to Dumbledore. "They were definitely somewhere around here ..."
"Lumos," Dumbledore said, lighting his wand and holding it up.
Its narrow beam traveled from black trunk to black trunk, illuminating the ground. And then it fell upon a pair of feet (GF28).
The narrow beam of the Lumos spell is also illustrated in GF9:
“What happened?” said Hermione anxiously, stopping so abruptly that Harry walked into her. “Ron, where are you? Oh this is stupid - lumos!”
She illuminated her wand and directed its narrow beam across the path. Ron was lying sprawled on the ground (GF9).