diff --git a/src/tiledimage.js b/src/tiledimage.js
index def57fae..d705240b 100644
--- a/src/tiledimage.js
+++ b/src/tiledimage.js
@@ -774,9 +774,25 @@ $.extend($.TiledImage.prototype, $.EventSource.prototype, /** @lends OpenSeadrag
      * @fires OpenSeadragon.TiledImage.event:opacity-change
      */
     setOpacity: function(opacity) {
+        if (opacity === this.opacity) {
+            return;
+        }
+
         this.opacity = opacity;
         this._needsDraw = true;
-        this.raiseEvent('opacity-change');
+        /**
+         * Raised when the TiledImage's opacity is changed.
+         * @event opacity-change
+         * @memberOf OpenSeadragon.TiledImage
+         * @type {object}
+         * @property {Number} opacity - The new opacity value.
+         * @property {OpenSeadragon.TiledImage} eventSource - A reference to the
+         * TiledImage which raised the event.
+         * @property {?Object} userData - Arbitrary subscriber-defined object.
+         */
+        this.raiseEvent('opacity-change', {
+            opacity: this.opacity
+        });
     },
 
     /**
@@ -833,9 +849,25 @@ $.extend($.TiledImage.prototype, $.EventSource.prototype, /** @lends OpenSeadrag
      * @fires OpenSeadragon.TiledImage.event:composite-operation-change
      */
     setCompositeOperation: function(compositeOperation) {
+        if (compositeOperation === this.compositeOperation) {
+            return;
+        }
+
         this.compositeOperation = compositeOperation;
         this._needsDraw = true;
-        this.raiseEvent('composite-operation-change');
+        /**
+         * Raised when the TiledImage's opacity is changed.
+         * @event composite-operation-change
+         * @memberOf OpenSeadragon.TiledImage
+         * @type {object}
+         * @property {String} compositeOperation - The new compositeOperation value.
+         * @property {OpenSeadragon.TiledImage} eventSource - A reference to the
+         * TiledImage which raised the event.
+         * @property {?Object} userData - Arbitrary subscriber-defined object.
+         */
+        this.raiseEvent('composite-operation-change', {
+            compositeOperation: this.compositeOperation
+        });
     },
 
     // private