diff --git a/code/modules/lighting/light_source.dm b/code/modules/lighting/light_source.dm
index 8322e14098..a54b2f0f84 100644
--- a/code/modules/lighting/light_source.dm
+++ b/code/modules/lighting/light_source.dm
@@ -11,13 +11,16 @@
 	var/lum_g
 	var/lum_b
 
-	var/list/effect_r
-	var/list/effect_g
-	var/list/effect_b
+	var/tmp/old_lum_r
+	var/tmp/old_lum_g
+	var/tmp/old_lum_b
+
+	var/list/effect_str
 	var/list/effect_turf
 
 	var/applied
 
+	var/vis_update		//Whetever we should smartly recalculate visibility. and then only update tiles that became (in) visible to us
 	var/needs_update
 	var/destroyed
 	var/force_update
@@ -38,9 +41,7 @@
 
 	parse_light_color()
 
-	effect_r = list()
-	effect_g = list()
-	effect_b = list()
+	effect_str = list()
 	effect_turf = list()
 
 	update()
@@ -67,9 +68,16 @@
 
 /datum/light_source/proc/force_update()
 	force_update = 1
-	if(!needs_update)
-		lighting_update_lights += src
+	if(!needs_update) //Incase we're already updating either way.
 		needs_update = 1
+		lighting_update_lights += src
+
+/datum/light_source/proc/vis_update()
+	if(!needs_update)
+		needs_update = 1
+		lighting_update_lights += src
+
+	vis_update = 1
 
 /datum/light_source/proc/check()
 	if(!source_atom || !light_range || !light_power)
@@ -96,14 +104,19 @@
 		light_range = source_atom.light_range
 		. = 1
 
+	if(light_range && light_power && !applied)
+		. = 1
+
+	if(. || source_atom.light_color != light_color)//Save the old lumcounts if we need to update, if the colour changed DO IT BEFORE we parse the colour and LOSE the old lumcounts!
+		old_lum_r = lum_r
+		old_lum_g = lum_g
+		old_lum_b = lum_b
+
 	if(source_atom.light_color != light_color)
 		light_color = source_atom.light_color
 		parse_light_color()
 		. = 1
 
-	if(light_range && light_power && !applied)
-		. = 1
-
 /datum/light_source/proc/parse_light_color()
 	if(light_color)
 		lum_r = GetRedPart(light_color) / 255
@@ -143,19 +156,18 @@
 				if(!strength) //Don't add turfs that aren't affected to the affected turfs.
 					continue
 
-				effect_r += round(lum_r * strength, LIGHTING_ROUND_VALUE)
-				effect_g += round(lum_g * strength, LIGHTING_ROUND_VALUE)
-				effect_b += round(lum_b * strength, LIGHTING_ROUND_VALUE)
+				strength = round(strength, LIGHTING_ROUND_VALUE)	//Screw sinking points.
+
+				effect_str += strength
 
 				T.lighting_overlay.update_lumcount(
-					round(lum_r * strength, LIGHTING_ROUND_VALUE),
-					round(lum_g * strength, LIGHTING_ROUND_VALUE),
-					round(lum_b * strength, LIGHTING_ROUND_VALUE)
+					lum_r * strength,
+					lum_g * strength,
+					lum_b * strength
 				)
+
 			else
-				effect_r += 0
-				effect_g += 0
-				effect_b += 0
+				effect_str += 0
 
 			if(!T.affecting_lights)
 				T.affecting_lights = list()
@@ -171,11 +183,60 @@
 			T.affecting_lights -= src
 
 		if(T.lighting_overlay)
-			T.lighting_overlay.update_lumcount(-effect_r[i], -effect_g[i], -effect_b[i])
+			var/str = effect_str[i]
+			T.lighting_overlay.update_lumcount(-str * old_lum_r, -str * old_lum_g, -str * old_lum_b)
 
 		i++
 
-	effect_r.Cut()
-	effect_g.Cut()
-	effect_b.Cut()
+	effect_str.Cut()
 	effect_turf.Cut()
+
+//Smartly updates the lighting, only removes lum from and adds lum to turfs that actually got changed.
+//This is for lights that need to reconsider due to nearby opacity changes.
+//Stupid dumb copy pasta because BYOND and speed.
+/datum/light_source/proc/smart_vis_update()
+	var/list/view[0]
+	for(var/turf/T in dview(light_range, source_turf, INVISIBILITY_LIGHTING))
+		view += T	//Filter out turfs.
+
+	//This is the part where we calculate new turfs (if any)
+	var/list/new_turfs = view - effect_turf //This will result with all the tiles that are added.
+	for(var/turf/T in new_turfs)
+		//Big huge copy paste from apply_lum() incoming because screw unreadable defines and screw proc call overhead.
+		if(T.lighting_overlay)
+			. = light_power * falloff(T.lighting_overlay)
+			if(!.) //Don't add turfs that aren't affected to the affected turfs.
+				continue
+
+			. = round(., LIGHTING_ROUND_VALUE)
+
+			effect_str += .
+
+			T.lighting_overlay.update_lumcount(
+				lum_r * .,
+				lum_g * .,
+				lum_b * .
+			)
+
+		else
+			effect_str += 0
+
+		if(!T.affecting_lights)
+			T.affecting_lights = list()
+
+		T.affecting_lights += src
+		effect_turf += T
+
+	var/list/old_turfs = effect_turf - view
+	for(var/turf/T in old_turfs)
+		//Insert not-so-huge copy paste from remove_lum().
+		var/idx = effect_turf.Find(T) //Get the index, luckily Find() is cheap in small lists like this. (with small I mean under a couple thousand len)
+		if(T.affecting_lights)
+			T.affecting_lights -= src
+
+		if(T.lighting_overlay)
+			var/str = effect_str[idx]
+			T.lighting_overlay.update_lumcount(-str * lum_r, -str * lum_g, -str * lum_b)
+
+		effect_turf.Cut(idx, idx + 1)
+		effect_str.Cut(idx, idx + 1)
diff --git a/code/modules/lighting/lighting_overlay.dm b/code/modules/lighting/lighting_overlay.dm
index a22023d983..ca9d9b391f 100644
--- a/code/modules/lighting/lighting_overlay.dm
+++ b/code/modules/lighting/lighting_overlay.dm
@@ -98,8 +98,3 @@
 	var/turf/T = loc
 	if(istype(T))
 		T.lighting_overlay = null
-
-		for(var/datum/light_source/D in T.affecting_lights) //Remove references to us on the light sources affecting us.
-			D.effect_r -= src
-			D.effect_g -= src
-			D.effect_b -= src
diff --git a/code/modules/lighting/lighting_process.dm b/code/modules/lighting/lighting_process.dm
index 1571c6e388..1c8361dbaf 100644
--- a/code/modules/lighting/lighting_process.dm
+++ b/code/modules/lighting/lighting_process.dm
@@ -10,12 +10,17 @@
 	lighting_update_lights = list()
 
 	for(var/datum/light_source/L in lighting_update_lights_old)
-		if(L.needs_update)
-			if(L.destroyed || L.check() || L.force_update)
-				L.remove_lum()
-				if(!L.destroyed) L.apply_lum()
-				L.force_update = 0
-			L.needs_update = 0
+		if(L.destroyed || L.check() || L.force_update)
+			L.remove_lum()
+			if(!L.destroyed)
+				L.apply_lum()
+
+		else if(L.vis_update)	//We smartly update only tiles that became (in) visible to use.
+			L.smart_vis_update()
+
+		L.vis_update = 0
+		L.force_update = 0
+		L.needs_update = 0
 
 		scheck()
 
@@ -24,8 +29,7 @@
 	lighting_update_overlays = list()
 
 	for(var/atom/movable/lighting_overlay/O in lighting_update_overlays_old)
-		if(O.needs_update)
-			O.update_overlay()
-			O.needs_update = 0
+		O.update_overlay()
+		O.needs_update = 0
 
 		scheck()
diff --git a/code/modules/lighting/lighting_turf.dm b/code/modules/lighting/lighting_turf.dm
index 0a438b047c..a7a5990709 100644
--- a/code/modules/lighting/lighting_turf.dm
+++ b/code/modules/lighting/lighting_turf.dm
@@ -4,7 +4,7 @@
 
 /turf/proc/reconsider_lights()
 	for(var/datum/light_source/L in affecting_lights)
-		L.force_update()
+		L.vis_update()
 
 /turf/proc/lighting_clear_overlays()
 	if(lighting_overlay)