diff --git a/lib/mess/renderer.js b/lib/mess/renderer.js
index 07e14f5..5550b3b 100644
--- a/lib/mess/renderer.js
+++ b/lib/mess/renderer.js
@@ -4,7 +4,8 @@ var path = require('path'),
     Step = require('step'),
     _ = require('underscore')._,
     sys = require('sys'),
-    mess = require('mess');
+    mess = require('mess'),
+    tree = require('mess/tree');
 
 require.paths.unshift(path.join(__dirname, '..', 'lib'));
 
@@ -211,7 +212,7 @@ mess.Renderer = function Renderer(env) {
             // definitions are ordered in specificity,
             // high to low
             //
-            // basically if 'this level' has 
+            // basically if 'this level' has
             // a filter, then keep going, otherwise
             // this is the final selector.
             var winners = [];
@@ -244,21 +245,34 @@ mess.Renderer = function Renderer(env) {
         },
 
         resolve_filters: function(definitions) {
-            var negated_filters = [];
+            var negatedFilters = [];
+            var negatedZoom = new tree.ZoomFilter('zoom', { value: '>=' }, '0');
+
             for (var i = 0; i < definitions.length; i++) {
-                if (definitions[i].selector.filters.length) {
-                    // array of the negation of this definition's filters
-                    var negation = definitions[i].selector.filters.map(
-                        function(f) { return f.negate(); });
+                var filters = definitions[i].selector.filters;
+                var normal = filters.filter(function(f) { return f instanceof tree.Filter; });
+                var zoom = filters.filter(function(f) { return f instanceof tree.ZoomFilter; });
 
-                    // add in existing negations
-                    // TODO: run uniq on this.
-                    definitions[i].selector.filters = 
-                        definitions[i].selector.filters.concat(negated_filters);
+                var negation = normal.map(function(f) { return f.negate(); });
 
-                    // add this definition's filter's negations to the list
-                    negated_filters = negated_filters.concat(negation);
-                }
+                // add in existing negations
+                // TODO: run uniq on this.
+                normal.push.apply(normal, negatedFilters);
+
+                // add this definition's filter's negations to the list
+                negatedFilters.push.apply(negatedFilters, negation);
+
+                // Merge all zoom filters without overwriting existing zoom
+                // filters; they might be referenced in other selectors.
+                var currentZoom = new tree.ZoomFilter('zoom', { value: '>=' }, '0');
+                zoom.forEach(function(f) { currentZoom.intersection(f); });
+
+                // Only add the negated current zoom when there actually are zoom filters.
+                var negation = zoom.length ? currentZoom.negated() : false;
+                currentZoom.intersection(negatedZoom);
+                if (negation) negatedZoom.intersection(negation);
+
+                definitions[i].selector.filters = normal.concat([currentZoom]);
             }
             return definitions;
         },
@@ -348,14 +362,14 @@ mess.Renderer = function Renderer(env) {
              * @param {Array} stylesheets the results of ruleHash().
              * @return Formalized layer definition with .styles = [].
              */
-            
+
             var rulesets = _.flatten(stylesheets.map(function(rulesets) {
                 return rulesets[2].toMSS();
             }));
 
             var output = [entities(entity_list)];
             // TODO: must change when background colors are available
-            output.push('<Map background-color="' 
+            output.push('<Map background-color="'
                     + "#ffffff"
                     // findBackground(stylesheets)
                     + '" srs="+proj=merc +a=6378137 +b=6378137 '
@@ -369,7 +383,7 @@ mess.Renderer = function Renderer(env) {
                 var matching = rulesets.filter(function(ruleset) {
                     return ruleset.selector.matches(l.id, classes);
                 });
-                
+
                 // matching is an array of matching selectors,
                 // in order from high specificity to low.
                 var by_symbolizer = that.split_symbolizers(matching);
@@ -391,7 +405,7 @@ mess.Renderer = function Renderer(env) {
             // output.push(references(entity_list));
             // output.push(stylesheet_tmpl(m));
             output.push('</Map>');
-            
+
             callback(null, output.join('\n'));
         },
 
diff --git a/lib/mess/tree/selector.js b/lib/mess/tree/selector.js
index f8239bb..5a0aebf 100644
--- a/lib/mess/tree/selector.js
+++ b/lib/mess/tree/selector.js
@@ -58,11 +58,25 @@ tree.Selector.prototype.combinedFilter = function() {
             return f instanceof tree.ZoomFilter;
     });
 
-    return normal_filters.length ?
-        '<Filter>' + normal_filters.map(function(f) {
+    var filters = [];
+    if (normal_filters.length) {
+        filters.push('<Filter>' + normal_filters.map(function(f) {
             return '(' + f.toXML().trim() + ')';
-        }).join(' and ') + '</Filter>'
-        : '<ElseFilter/>';
+        }).join(' and ') + '</Filter>');
+    }
+
+    if (zoom_filters.length) {
+        filters.push(zoom_filters.map(function(f) {
+            return f.toXML();
+        }));
+    }
+
+    if (!filters.length) {
+        return '<ElseFilter/>';
+    }
+    else {
+        return filters.join('');
+    }
 };
 
 })(require('mess/tree'));
diff --git a/lib/mess/tree/zoomfilter.js b/lib/mess/tree/zoomfilter.js
index d21a2f9..1dcba42 100644
--- a/lib/mess/tree/zoomfilter.js
+++ b/lib/mess/tree/zoomfilter.js
@@ -1,11 +1,41 @@
 (function(tree) {
 
-tree.ZoomFilter = function(key, op, val, index) {
-    this.key = key;
-    this.op = op;
-    this.val = parseInt(val);
-    this.index = index;
-    this.zoom_range = tree.ZoomFilter.create_range(this.op.value, this.val);
+tree.ZoomFilter = function(key, op, value, index) {
+    value = parseInt(value);
+    if (value > tree.ZoomFilter.maxZoom || value < 0) {
+        throw {
+            message: 'Only zoom levels between 0 and ' + tree.ZoomFilter.maxZoom + ' supported.',
+            index: index
+        };
+    }
+    this.range = tree.ZoomFilter.createRange(op.value, value);
+};
+
+tree.ZoomFilter.maxZoom = 22;
+
+tree.ZoomFilter.ranges = {
+     1: 500000000,
+     2: 200000000,
+     3: 100000000,
+     4: 50000000,
+     5: 25000000,
+     6: 12500000,
+     7: 6500000,
+     8: 3000000,
+     9: 1500000,
+    10: 750000,
+    11: 400000,
+    12: 200000,
+    13: 100000,
+    14: 50000,
+    15: 25000,
+    16: 12500,
+    17: 5000,
+    18: 2500,
+    19: 1000,
+    20: 500,
+    21: 250,
+    22: 100
 };
 
 /**
@@ -13,30 +43,46 @@ tree.ZoomFilter = function(key, op, val, index) {
  * which denotes whether this filter should apply
  * to each of the zoom levels from 0-22.
  */
-tree.ZoomFilter.create_range = function(op, value) {
-    var max_zoom = 22;
-    var zoom_range = [];
+tree.ZoomFilter.createRange = function(op, value) {
+    var range = [];
     if (op === '>' || op === '>=') {
         if (op === '>') value++;
-        for (var i = 0; i < max_zoom; i++) {
-            zoom_range[i] = (i >= value);
+        for (var i = 0; i < tree.ZoomFilter.maxZoom; i++) {
+            range[i] = (i >= value);
         }
     } else {
         if (op === '<') value--;
-        for (var i = 0; i < max_zoom; i++) {
-            zoom_range[i] = (i <= value);
+        for (var i = 0; i < tree.ZoomFilter.maxZoom; i++) {
+            range[i] = (i <= value);
         }
     }
-    return zoom_range;
+    return range;
 };
 
+/**
+ * Returns an array of ranges that are set.
+ */
+tree.ZoomFilter.getRanges = function(range) {
+    var ranges = [], start = null;
+    for (var i = 0; i < range.length; i++) {
+        if (start == null && range[i]) {
+            start = i;
+        } else if (start != null && !range[i]) {
+            ranges.push([start, i - 1]);
+            start = null;
+        }
+    }
+    if (start != null) ranges.push([start, 22]);
+    return ranges;
+}
+
 /**
  * Find the overlap of this and another set
  */
 tree.ZoomFilter.prototype.intersection = function(filter) {
-    if (filter.zoom_range) {
-        for (var i = 0; i < this.max_zoom; i++) {
-            this.zoom_range[i] = this.zoom_range[i] && filter.zoom_range[i];
+    if (filter.range) {
+        for (var i = 0; i < this.range.length; i++) {
+            this.range[i] = this.range[i] && filter.range[i];
         }
     }
 };
@@ -45,9 +91,9 @@ tree.ZoomFilter.prototype.intersection = function(filter) {
  * Find the union of this and another set
  */
 tree.ZoomFilter.prototype.union = function(filter) {
-    if (filter.zoom_range) {
-        for (var i = 0; i < this.max_zoom; i++) {
-            this.zoom_range[i] = this.zoom_range[i] || filter.zoom_range[i];
+    if (filter.range) {
+        for (var i = 0; i < this.range.length; i++) {
+            this.range[i] = this.range[i] || filter.range[i];
         }
     }
 };
@@ -60,58 +106,26 @@ tree.ZoomFilter.prototype.union = function(filter) {
  * Usage is for doing the equivalent of an ElseFilter
  * for defaulting to non-zoom-filtered rules
  */
-tree.ZoomFilter.prototype.negate = function() {
-    this.zoom_range = this.zoom_range.map(function(i) {
+tree.ZoomFilter.prototype.negated = function() {
+    var negated = this.clone();
+    negated.range = this.range.map(function(i) {
         return !i;
     });
-    return this;
+    return negated;
 };
 
 tree.ZoomFilter.prototype.toXML = function(env) {
-    if (this.val > 22 || this.val < 0) {
-        throw {
-            message: 'Only zoom levels between 0 and 22 supported.',
-            index: this.index
-        };
-    }
-
-    var zooms = {
-      '1': [200000000, 500000000],
-      '2': [100000000, 200000000],
-      '3': [50000000, 100000000],
-      '4': [25000000, 50000000],
-      '5': [12500000, 25000000],
-      '6': [6500000, 12500000],
-      '7': [3000000, 6500000],
-      '8': [1500000, 3000000],
-      '9': [750000, 1500000],
-     '10': [400000, 750000],
-     '11': [200000, 400000],
-     '12': [100000, 200000],
-     '13': [50000, 100000],
-     '14': [25000, 50000],
-     '15': [12500, 25000],
-     '16': [5000, 12500],
-     '17': [2500, 5000],
-     '18': [1000, 2500],
-     '19': [500, 1000],
-     '20': [250, 500],
-     '21': [100, 250],
-     '22': [50, 100]};
-
-    switch (this.op.value) {
-        case '>':
-            return '<MaxScaleDenominator>' + zooms[this.val][0] +
-                '</MaxScaleDenominator>';
-        case '>=':
-            return '<MaxScaleDenominator>' + zooms[this.val][1] +
-                '</MaxScaleDenominator>';
-        case '<':
-            return '<MinScaleDenominator>' + zooms[this.val][1] +
-                '</MinScaleDenominator>';
-        case '<=':
-            return '<MinScaleDenominator>' + zooms[this.val][0] +
-                '</MinScaleDenominator>';
-    }
+    var ranges = tree.ZoomFilter.getRanges(this.range);
+    return ranges.map(function(range) {
+        return (range[0] > 0 ? '<MinScaleDenominator>' + /*tree.ZoomFilter.ranges[*/range[0]/*]*/ + '</MinScaleDenominator>' : '') +
+               (range[1] < 22 ? '<MaxScaleDenominator>' + /*tree.ZoomFilter.ranges[*/range[1]/*]*/ + '</MaxScaleDenominator>' : '');
+    });
 };
+
+tree.ZoomFilter.prototype.clone = function() {
+    var obj = Object.create(Object.getPrototypeOf(this));
+    obj.range = this.range.slice();
+    return obj;
+}
+
 })(require('mess/tree'));