Why does the whole square the light is in light up?

Hi everyone,

i am trying to make an explosion with a light effect but whenever the projectile explodes the whole square the explosion is above lights up and not just a radius around the explosion:-(

datablock ExplosionData(TankPrimaryExplosion)
{
   soundProfile = TankPrimaryExplosionSound;
   lifeTimeMS = 1200;

   // Volume particles
   particleEmitter = TankPrimaryExplosionFireEmitter;
   particleDensity = 75;
   particleRadius = 2;

   // Point emission
   emitter[0] = TankPrimaryExplosionSmokeEmitter;
   emitter[1] = TankPrimaryExplosionSparkEmitter;

   // Sub explosion objects
   subExplosion[0] = TankPrimarySubExplosion1;
   subExplosion[1] = TankPrimarySubExplosion2;
   
   // Camera Shaking
   shakeCamera = true;
   camShakeFreq = "10.0 11.0 10.0";
   camShakeAmp = "1.0 1.0 1.0";
   camShakeDuration = 0.5;
   camShakeRadius = 10.0;

   // Exploding debris
   debris = TankPrimaryExplosionDebris;
   debrisThetaMin = 0;
   debrisThetaMax = 60;
   debrisPhiMin = 0;
   debrisPhiMax = 360;
   debrisNum = 6;
   debrisNumVariance = 2;
   debrisVelocity = 1;
   debrisVelocityVariance = 0.5;
   
   // Impulse
   impulseRadius = 10;
   impulseForce = 15;

   // Dynamic light
   lightStartRadius = 6;
   lightEndRadius = 3;
   lightStartColor = "0.5 0.5 0";
   lightEndColor = "0 0 0";
};

this is my explosion datablock

does anyone have a clue what i am doing wrong?

do i have to use a shapebase image to make the light work correctly?