Don't set zoomOffset - maxResolution and numZoomLevels is enough. r=fredj (closes http://trac.osgeo.org/openlayers/ticket/3550)

lib/OpenLayers/Layer/Bing.js

@@ -144,7 +144,6 @@ OpenLayers.Layer.Bing = OpenLayers.Class(OpenLayers.Layer.XYZ, {
             maxResolution: Math.min(
                 this.serverResolutions[res.zoomMin], this.maxResolution
             ),
-            zoomOffset: res.zoomMin,
             numZoomLevels: Math.min(
                 res.zoomMax + 1 - res.zoomMin, this.numZoomLevels
             )

tests/Layer/Bing.html

@@ -41,7 +41,7 @@
         var origProcessMetadata = OpenLayers.Layer.Bing.processMetadata;
         OpenLayers.Layer.Bing.processMetadata = function(metadata) {
             meta.push(metadata);
-        }
+        };
         map = new OpenLayers.Map("map");
         layer = new OpenLayers.Layer.Bing(options);
         var extent;
@@ -98,6 +98,22 @@
             map.destroy();
         });
     }
+    
+    function test_getXYZ(t) {
+        t.plan(1);
+        
+        var map = new OpenLayers.Map("map", {allOverlays: true});
+        var osm = new OpenLayers.Layer.OSM();
+        map.addLayer(osm);
+        map.zoomToExtent(new OpenLayers.Bounds(11373579,-2445208,13628777,680760));
+        layer = new OpenLayers.Layer.Bing(options);
+        map.addLayer(layer);
+        
+        t.delay_call(2, function() {
+            var xyz = layer.getXYZ(layer.getTileBounds(new OpenLayers.Pixel(1,1)));
+            t.eq(xyz.z, OpenLayers.Util.indexOf(layer.serverResolutions, map.getResolution()), "zoom level correct");
+        });
+    }
 
     function test_clone(t) {
         t.plan(1);