diff --git a/src/lua_baselib.c b/src/lua_baselib.c
index c1fd87af3..840863eb0 100644
--- a/src/lua_baselib.c
+++ b/src/lua_baselib.c
@@ -1809,9 +1809,10 @@ static int lib_pFadeLight(lua_State *L)
 	INT16 tag = (INT16)luaL_checkinteger(L, 1);
 	INT32 destvalue = (INT32)luaL_checkinteger(L, 2);
 	INT32 speed = (INT32)luaL_checkinteger(L, 3);
+	boolean ticbased = lua_optboolean(L, 4);
 	NOHUD
 	INLEVEL
-	P_FadeLight(tag, destvalue, speed);
+	P_FadeLight(tag, destvalue, speed, ticbased);
 	return 0;
 }
 
diff --git a/src/p_lights.c b/src/p_lights.c
index 8aa2eedca..95171155e 100644
--- a/src/p_lights.c
+++ b/src/p_lights.c
@@ -13,6 +13,7 @@
 ///        Fire flicker, light flash, strobe flash, lightning flash, glow, and fade.
 
 #include "doomdef.h"
+#include "doomstat.h" // gametic
 #include "p_local.h"
 #include "r_state.h"
 #include "z_zone.h"
@@ -322,40 +323,57 @@ glow_t *P_SpawnAdjustableGlowingLight(sector_t *minsector, sector_t *maxsector,
 	return g;
 }
 
-/** Fades all the lights in sectors with a particular tag to a new
+/** Fades all the lights in specified sector to a new
   * value.
   *
-  * \param tag       Tag to look for sectors by.
+  * \param sector    Target sector
   * \param destvalue The final light value in these sectors.
   * \param speed     Speed of the fade; the change to the ligh
   *                  level in each sector per tic.
-  * \todo Calculate speed better so that it is possible to specify
-  *       the time for completion of the fade, and all lights fade
-  *       in this time regardless of initial values.
+  * \param ticbased  Use a specific duration for the fade, defined by speed
   * \sa T_LightFade
   */
-void P_FadeLight(INT16 tag, INT32 destvalue, INT32 speed)
+void P_FadeLightBySector(sector_t *sector, INT32 destvalue, INT32 speed, boolean ticbased)
+{
+	lightlevel_t *ll;
+
+	P_RemoveLighting(sector); // remove the old lighting effect first
+
+	if ((ticbased && !speed) || sector->lightlevel == destvalue) // set immediately
+	{
+		sector->lightlevel = destvalue;
+		return;
+	}
+
+	ll = Z_Calloc(sizeof (*ll), PU_LEVSPEC, NULL);
+	ll->thinker.function.acp1 = (actionf_p1)T_LightFade;
+	sector->lightingdata = ll; // set it to the lightlevel_t
+
+	P_AddThinker(&ll->thinker); // add thinker
+
+	ll->sector = sector;
+	ll->sourcelevel = sector->lightlevel;
+	ll->destlevel = destvalue;
+
+	if (ticbased)
+	{
+		ll->ticbased = true;
+		ll->timer = ll->speed = abs(speed); // use ll->speed for total duration
+	}
+	else
+	{
+		ll->ticbased = false;
+		ll->timer = -1;
+		ll->speed = abs(speed);
+	}
+}
+
+void P_FadeLight(INT16 tag, INT32 destvalue, INT32 speed, boolean ticbased)
 {
 	INT32 i;
-	lightlevel_t *ll;
-	sector_t *sector;
-
 	// search all sectors for ones with tag
 	for (i = -1; (i = P_FindSectorFromTag(tag, i)) >= 0 ;)
-	{
-		sector = &sectors[i];
-
-		P_RemoveLighting(sector); // remove the old lighting effect first
-		ll = Z_Calloc(sizeof (*ll), PU_LEVSPEC, NULL);
-		ll->thinker.function.acp1 = (actionf_p1)T_LightFade;
-		sector->lightingdata = ll; // set it to the lightlevel_t
-
-		P_AddThinker(&ll->thinker); // add thinker
-
-		ll->sector = sector;
-		ll->destlevel = destvalue;
-		ll->speed = speed;
-	}
+		P_FadeLightBySector(&sectors[i], destvalue, speed, ticbased);
 }
 
 /** Fades the light level in a sector to a new value.
@@ -365,18 +383,37 @@ void P_FadeLight(INT16 tag, INT32 destvalue, INT32 speed)
   */
 void T_LightFade(lightlevel_t *ll)
 {
+	if (ll->ticbased)
+	{
+		if (--ll->timer <= 0)
+		{
+			ll->sector->lightlevel = ll->destlevel; // set to dest lightlevel
+			P_RemoveLighting(ll->sector); // clear lightingdata, remove thinker
+		}
+		else
+		{
+			INT16 delta = abs(ll->destlevel - ll->sourcelevel);
+			fixed_t factor = min(FixedDiv(ll->speed - ll->timer, ll->speed), 1*FRACUNIT);
+			if (ll->destlevel < ll->sourcelevel)
+				ll->sector->lightlevel = max(min(ll->sector->lightlevel, ll->sourcelevel - (INT16)FixedMul(delta, factor)), ll->destlevel);
+			else if (ll->destlevel > ll->sourcelevel)
+				ll->sector->lightlevel = min(max(ll->sector->lightlevel, ll->sourcelevel + (INT16)FixedMul(delta, factor)), ll->destlevel);
+		}
+		return;
+	}
+
 	if (ll->sector->lightlevel < ll->destlevel)
 	{
 		// increase the lightlevel
 		if (ll->sector->lightlevel + ll->speed >= ll->destlevel)
 		{
 			// stop changing light level
-			ll->sector->lightlevel = (INT16)ll->destlevel; // set to dest lightlevel
+			ll->sector->lightlevel = ll->destlevel; // set to dest lightlevel
 
 			P_RemoveLighting(ll->sector); // clear lightingdata, remove thinker
 		}
 		else
-			ll->sector->lightlevel = (INT16)(ll->sector->lightlevel + (INT16)ll->speed); // move lightlevel
+			ll->sector->lightlevel += ll->speed; // move lightlevel
 	}
 	else
 	{
@@ -384,11 +421,11 @@ void T_LightFade(lightlevel_t *ll)
 		if (ll->sector->lightlevel - ll->speed <= ll->destlevel)
 		{
 			// stop changing light level
-			ll->sector->lightlevel = (INT16)ll->destlevel; // set to dest lightlevel
+			ll->sector->lightlevel = ll->destlevel; // set to dest lightlevel
 
 			P_RemoveLighting(ll->sector); // clear lightingdata, remove thinker
 		}
 		else
-			ll->sector->lightlevel = (INT16)(ll->sector->lightlevel - (INT16)ll->speed); // move lightlevel
+			ll->sector->lightlevel -= ll->speed; // move lightlevel
 	}
 }
diff --git a/src/p_saveg.c b/src/p_saveg.c
index 42757faf2..574f871bb 100644
--- a/src/p_saveg.c
+++ b/src/p_saveg.c
@@ -1559,8 +1559,11 @@ static void SaveLightlevelThinker(const thinker_t *th, const UINT8 type)
 	const lightlevel_t *ht = (const void *)th;
 	WRITEUINT8(save_p, type);
 	WRITEUINT32(save_p, SaveSector(ht->sector));
-	WRITEINT32(save_p, ht->destlevel);
-	WRITEINT32(save_p, ht->speed);
+	WRITEINT16(save_p, ht->sourcelevel);
+	WRITEINT16(save_p, ht->destlevel);
+	WRITEINT16(save_p, ht->speed);
+	WRITEUINT8(save_p, (UINT8)ht->ticbased);
+	WRITEINT32(save_p, ht->timer);
 }
 
 //
@@ -2532,8 +2535,11 @@ static inline void LoadLightlevelThinker(actionf_p1 thinker)
 	lightlevel_t *ht = Z_Malloc(sizeof (*ht), PU_LEVSPEC, NULL);
 	ht->thinker.function.acp1 = thinker;
 	ht->sector = LoadSector(READUINT32(save_p));
-	ht->destlevel = READINT32(save_p);
-	ht->speed = READINT32(save_p);
+	ht->sourcelevel = READINT16(save_p);
+	ht->destlevel = READINT16(save_p);
+	ht->speed = READINT16(save_p);
+	ht->ticbased = (boolean)READUINT8(save_p);
+	ht->timer = READINT32(save_p);
 	if (ht->sector)
 		ht->sector->lightingdata = ht;
 	P_AddThinker(&ht->thinker);
diff --git a/src/p_spec.c b/src/p_spec.c
index 40be3c7fb..85790041f 100644
--- a/src/p_spec.c
+++ b/src/p_spec.c
@@ -2778,7 +2778,16 @@ static void P_ProcessLineSpecial(line_t *line, mobj_t *mo, sector_t *callsec)
 			break;
 
 		case 420: // Fade light levels in tagged sectors to new value
-			P_FadeLight(line->tag, line->frontsector->lightlevel, P_AproxDistance(line->dx, line->dy)>>FRACBITS);
+			P_FadeLight(line->tag,
+				(line->flags & ML_DONTPEGBOTTOM) ? max(sides[line->sidenum[0]].textureoffset>>FRACBITS, 0) : line->frontsector->lightlevel,
+				// failsafe: if user specifies Back Y Offset and NOT Front Y Offset, use the Back Offset
+				// to be consistent with other light and fade specials
+				(line->flags & ML_DONTPEGBOTTOM) ?
+					((line->sidenum[1] != 0xFFFF && !(sides[line->sidenum[0]].rowoffset>>FRACBITS)) ?
+						max(min(sides[line->sidenum[1]].rowoffset>>FRACBITS, 255), 0)
+						: max(min(sides[line->sidenum[0]].rowoffset>>FRACBITS, 255), 0))
+					: abs(P_AproxDistance(line->dx, line->dy))>>FRACBITS),
+				(line->flags & ML_EFFECT4));
 			break;
 
 		case 421: // Stop lighting effect in tagged sectors
diff --git a/src/p_spec.h b/src/p_spec.h
index e0bcc18eb..69087d6c4 100644
--- a/src/p_spec.h
+++ b/src/p_spec.h
@@ -136,8 +136,13 @@ typedef struct
 {
 	thinker_t thinker; ///< Thinker in use for the effect.
 	sector_t *sector;  ///< Sector where action is taking place.
-	INT32 destlevel;   ///< Light level we're fading to.
-	INT32 speed;       ///< Speed at which to change light level.
+	INT16 sourcelevel; ///< Light level we're fading from.
+	INT16 destlevel;   ///< Light level we're fading to.
+	INT16 speed;       ///< Speed at which to change light level. OR: Tic-based duration
+
+	// Tic-based behavior
+	boolean ticbased;  ///< Tic-based logic
+	INT32 timer;       ///< Tic-based timer
 } lightlevel_t;
 
 #define GLOWSPEED 8
@@ -156,7 +161,8 @@ strobe_t * P_SpawnAdjustableStrobeFlash(sector_t *minsector, sector_t *maxsector
 void T_Glow(glow_t *g);
 glow_t *P_SpawnAdjustableGlowingLight(sector_t *minsector, sector_t *maxsector, INT32 length);
 
-void P_FadeLight(INT16 tag, INT32 destvalue, INT32 speed);
+void P_FadeLightBySector(sector_t *sector, INT32 destvalue, INT32 speed, boolean ticbased);
+void P_FadeLight(INT16 tag, INT32 destvalue, INT32 speed, boolean ticbased);
 void T_LightFade(lightlevel_t *ll);
 
 typedef enum