When a story wants to demonstrate a light is blindingly bright, it's often impractical to have it illuminate in an additive way on top of the ambient lighting. Just making a scene brighter doesn't look that impactful (base color palettes are already pretty bright), and lightening everything further can make the visuals less dramatic, not more.
Instead, artists will generally increase the contrast of the shading to represent how bright a light is, with brighter lights somehow generating shadows that overwrite the existing lighting.
Needless to say, this is not how light works in real life, which can lead to some strange consequences. At it's most absurd, the addition of a light source may darken the subject it's trying to illuminate.
Sometimes this effect is meant to represent the difficulty our eyes have adjusting to bright lights by obscuring the newly created shadowed area. It's also often a consequence of standard color correction efforts. Ironically, extreme brightness doesn't feel bright unless something else is made darker for juxtaposition and context.
Even in flat cartoon art that normally lacks shading, bright lights may create dark shadows that don't exist anywhere else in the work. This can be used for situational effects, such as to makes explosions look more cool. This is also fairly common when characters get electrocuted, and may be combined with X-Ray Sparks. It might also be a property of a Battle Aura. When taken to its logical extreme with flash grenades/nuclear explosions, shadows often will become pitch black.
See also Hollywood Darkness, which also plays with our expectations of light.
Subtrope of Chiaroscuro.
Examples:
- Dragon Ball: Energy blasts are often shown this way. During really dramatic ones, the entire scene may be illuminated only by the blast, as if the Sun were momentarily switched off.
- Fairy Tail: Laxus' lightning powers can manifest a dark shading around him while charging up the electricity.
- Fate/Zero: Gilgimesh's Gate Of Babylon shines a dramatic shadow over him whenever he activates it.
- Hunter × Hunter: The animators occasionally apply darkened shadows to Killua's lightning attacks to make them more dramatic. He gets a continuous version while activating Godspeed.
- JoJo's Bizarre Adventure:
- Battle Tendency: On the cusp of sunrise alongside the usage of UV lights, Kars becoming the Ultimate Lifeform manifest light strong enough to produce shadows in brightness.
- Stardust Crusaders: When DIO reveals himself to Polnareff prior to the last battle, he is accompanied by a Holy Backlight illuminating the entire hallway.
- Diamond is Unbreakable: Yoshikage Kira's explosive bombs produce a brief darkened effect even in a lit area.
- Golden Wind: When Polnareff briefly impales his Stand with the arrow, the effect causes a luminous light to emerge with surrounding shading.
- Stone Ocean: Upon Pucci awakening Made In Heaven, his entire body emits streams of light that cast enough shadow in broad daylight.
- Naruto: Lightning release illuminates with darkened shadows, particularly when Sasuke uses it.
- One Piece: Borsalino's light powers manifest very dark shading even in broad daylight.
- ANNO: Mutationem: When Ann activates her Super Mode for the first time, she gets surrounded by an aura of light that encompasses her whole body, brightly illuminating the area with a bit of shadow even with sunlight coming in from above.
- Paranatural: Spenders light powers cast impossibly dark shadows although this might be justified by his secondary power-set.
- Avatar:
- Avatar: The Last Airbender: Lightning-bending can darken character shadows, notably when Iroh first demonstrates it to Zuko and again when Azula strikes Zuko in the finale.
- The Legend of Korra: In the series finale when Korra creates a new spirit portal, the purple explosion that engulfs the city darkens everyone's shadows to near black.
- The Fairly OddParents!: Does this when invoking Scary Flashlight Face in broad daylight. It's also done more naturally during occasional explosions that are meant to look cinematic, casting a shadow that would not exist.
- My Little Pony: Friendship Is Magic: Discord throws a glass of chocolate milk that explodes casting a dark shadow this way, though given the character it's hard to know if the implausibility was intentional.
- Spongebob Squarepants: Various explosions and bright lights creates shadows, most memorably when King Neptune's bald head shown so brightly it blinded everyone around him.
Bystander Fish: MY EYES!
- Steven Universe: White Diamond's head chamber has darkened shadows manifesting in her head. The character makes it even more intense at one point as a demonstration of her own brilliant light.
- Teen Titans (2003): Dr Light's flash grenades operate this way, creating a black-and-white flash.
- X-Men: Evolution: Storm's lightning attacks create darker shadows upon striking people, as does Rogue's version when she's copying her powers during their fight.
