To improve performance, do not use drop-shadows on your series items unless they are necessary. You can selectively add shadows to individual chart series by using renderers such as the ShadowBoxItemRenderer and ShadowLineRenderer classes.

Shadows are implemented as filters in charting controls. As a result, you must remove these shadows by setting the chart control's seriesFilters property to an empty Array. The following example removes the shadows from all series, but then changes the renderer for the third series to be a shadow renderer:

<?xml version="1.0"?>
<!-- optimize/RemoveShadowsColumnChart.mxml -->
<mx:Application xmlns:mx="http://www.adobe.com/2006/mxml">
    <mx:Script><![CDATA[
        import mx.collections.ArrayCollection;
        [Bindable]
        public var expenses:ArrayCollection = new ArrayCollection([
            {Month: "Jan", Income: 2000, Expenses: 1500, Profit: 500}, 
            {Month: "Feb", Income: 1000, Expenses: 200, Profit: 800},
            {Month: "Mar", Income: 1500, Expenses: 500, Profit: 1000}
        ]);
    ]]></mx:Script>
    <mx:Panel title="Column Chart">
        <mx:ColumnChart id="myChart" dataProvider="{expenses}">
            <mx:seriesFilters>
                <mx:Array/>
            </mx:seriesFilters>
            <mx:horizontalAxis>
                <mx:CategoryAxis dataProvider="{expenses}" categoryField="Month"/>
            </mx:horizontalAxis>
            <mx:series>
                <mx:ColumnSeries xField="Month" yField="Income" displayName="Income"/>
                <mx:ColumnSeries xField="Month" yField="Expenses" displayName="Expenses"/>
                <mx:ColumnSeries xField="Month" yField="Profit" displayName="Profit" itemRenderer="mx.charts.renderers.ShadowBoxItemRenderer"/>
            </mx:series>
        </mx:ColumnChart>
        <mx:Legend dataProvider="{myChart}"/>
    </mx:Panel>
</mx:Application>
The executing SWF file for the previous example is shown below: