You can set transparency universally on a layer, or you can vary transparency by an attribute or an expression. Varying the transparency of symbols is a way to indicate variations in magnitude of an attribute. For example, polygon symbols representing election results can have transparency set relative to the percentage of the total population that cast a ballot.
You can also adjust the transparency of any color in any symbol. While theoretically you can combine these approaches together in a map, be aware that the result may be visually difficult to comprehend. Use these techniques judiciously.
Set the transparency of a layer universally
- Select a feature layer in the Contents pane.
- Under Feature Layer, on the Appearance tab, in the Effects group, adjust the Layer Transparency slider or type a transparency percentage.
Set the transparency variable to a field or an expression
You can refine layer symbology by setting the transparency variable to a field or an expression.
- Select the feature layer in the Contents pane.
- On the Appearance tab, in the Drawing group, click Symbology .
- In the Symbology pane, on the Vary symbology by attribute tab , expand the Transparency heading and do one of the following:
- Choose a numeric field from the Field menu to vary the transparency.
- Write an expression to determine transparency. Choose Custom from the Field menu, or click the Set an expression button to open the Expression Builder dialog box. Write an expression and click Verify to validate it. Note that although an expression is valid, it may not return a valid numeric value for the transparency variable. You can filter the Expression Builder dialog box to show only numeric fields to help prevent this.
- Optionally, choose a Normalization field. Normalization is only available when the transparency variable is set to a field. It is not available when the transparency variable is set to an expression.
- Specify the high and low values and optionally adjust the histogram. See Histograms for more information.
- Check the Show legend check box to add a representation of the transparency variation to the layer's legend in both the Contents pane and any legends placed on layouts.
- To remove the transparency variable or the normalization field, choose <none> from the Field or Normalization menus, respectively.
Expressions are not saved by the layer if you change the transparency variable to read from a field instead of an expression. You can save the expression from the Expression Builder dialog box by clicking Export before making changes.