Creating Matte Layers

Deke

I use Daz for animation and sometimes create a black layer to use in post production. A couple questions:

1) Often the matte layer doesn't exactly match the full Iray rendered layer. I render in PNG files. The Matte layer is simply a Viewport export with all the lights turned out (forming a black sillhouette of a character). Can't understand why the shape and position of the export isn't an identical match to the Iray-rendered layer.

2) Some elements don't go black even with the lights turned out. Often eyes, lashes, hair, and occasional wardrobe items are gray intead of black. Any idea what surface setting might cause and item to not be opaque?  

Artini

For 1)

Do you set the render engine to Viewport and then press render to get the image?

I use this technique with FilaToon renders and has not noticed any difference from iray renders,