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The Displays tab shows the outputs for the selected pass.  They are in the list on the right.  The default output of the Final pass is, as you might expect, rgba, the color (Ci) and alpha (a) channels of a typical image. You can add other outputs by selecting from the list of presets in the list on the left and clicking the arrow button between the lists.  Custom  Custom outputs can also be added by clicking the '+' button at the bottom of the lists.

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