Transparency can be used for any symbolization type,
but it is especially useful for drawing raster layers with other layers on your map. This allows you to see the raster layer while still viewing underlying layers.
To adjust the transparency of a layer
1. In the Contents window, right-click the layer whose transparency you want to adjust. A slider bar appears which you can move to adjust the transparency of the layer and, depending on how you've set your Options, layers above it.
2. Move the slider bar to adjust the transparency; the higher the percentage, the more transparent the layer.
Use Swipe to reveal layers beneath the layer you chose to swipe and, depending on how you've set your Options, the layers above it. This command makes it easy to quickly see what is underneath a particular layer without having to turn it off in the table of contents or reorder layers.
To reveal layers beneath the layer you've selected
Choose the layer or group layer you want to swipe from the Contents, then move the cursor over the map. You'll notice that the cursor changes
based on whether you are resting the mouse pointer onthe top, bottom, left, or right of the map.
This lets you choose the direction in which you want to swipe the layer. Hold down the left mouse button and drag in the direction indicated by the mouse pointer.
Tip With the Swipe tool selected, holding down the Ctrl or Shift key and clicking the mouse will flicker the selected layer on and off manually. The selected layer is off as long as you hold down the mouse. Flicker is particularly useful for temporal change detection (especially of satellite images or air photographs taken at different times of the same location), data quality comparison, and other analysis where you want to see the difference between layers. Fast rates of flicker can be used to make differences between layers appear to jump out due to the optical effect of the eye being attracted to changes between rapidly alternating displays (an effect also exploited by the early experiments in cinematography).