Nighteye in Oblivion sadly doesn't have magnitude like it did in Morrowind, and custom shaders are something I haven't yet tackled.
However, I think there's a mod which already does this. Stealth Overhaul?
Edit: Oh, and happy birthday to me.
ALTERATION Bending the Mundus; mass, external energy, physical forces.Burden/FeatherChameleonOpenResist [Elements][All] Shield[s]TelekinesisWater WalkingWeakness to [Elements]CONJURATION Transport from/through Oblivion; binding of extraplanar forces.Bound [All]Summon [All]Turn UndeadDESTRUCTION Barely-filtered Aetherius; raw energy, radiance, entropy.Disintegrate [All][Element] DamageLightILLUSION Manipulation of thoughts and subjective perception.CalmCharmCommand [All]DemoralizeDrain [All]FrenzyInvisibilityRallySilenceMYSTICISM Bending the Aurbis; souls, transferrence, metaphysical forces.Absorb [All]DispelDetect LifeReflect DamageReflect SpellResist MagicSpell AbsorptionSoul TrapWeakness to MagicRESTORATION Manipulating the physical and metaphysical processes of life.Cure [All]Damage [All]Fortify [All]Night-EyeParalyzeResist [Disease, Normal Weapons, Paralysis, Poison]Restore [All]Water BreathingWeakness to [Disease, Normal Weapons, Poison]
ALTERATION Bending the Mundus; mass, external energy, physical forces.Burden/FeatherChameleonOpenResist [Elements][All] Shield[s]TelekinesisWater WalkingWeakness to [Elements]CONJURATION Transport from/through Oblivion; binding of extraplanar forces.Bound [All]Summon [All]Turn UndeadDESTRUCTION Barely-filtered Aetherius; raw energy, radiance, entropy.Disintegrate [All][Element] DamageLightILLUSION Manipulation of thoughts and subjective perception.CalmCharmCommand [All]DemoralizeDrain [All]FrenzyInvisibilityRallySilenceMYSTICISM Bending the Aurbis; souls, transferrence, metaphysical forces.Absorb [All]DispelDetect LifeReflect DamageReflect SpellResist MagicSpell AbsorptionSoul TrapWeakness to MagicRESTORATION Manipulating the physical and metaphysical processes of life.Cure [All]Damage [All]Fortify [All]Night-EyeParalyzeResist [Disease, Normal Weapons, Paralysis, Poison]Restore [All]Water BreathingWeakness to [Disease, Normal Weapons, Poison]