Select the colour space that you want to use to isolate the edge.
Result Output box
Select Result to output the composite of the input image, input matte, and the matte generated by the edge detection. Or,
select Edge Only to output only the result of compositing the input image with the matte generated by the edge detection.
Matte Output button
Select Input to output the input matte or Edge Matte to output the matte generated by the edge detection.