Quote - DS does use displacement - but contrary to Poser it does have + and - settings. A nice tutorial is here:
forum.daz3d.com/viewtopic.php

As for advanced materials for DS - Elite Human Surface Shader (EHSS) is free, because it does come with S4 Elite:
www.daz3d.com/i/3d-models/-/stephanie-4-elite

Actually, it is DS that is limited, not Poser. Poser can do maps that are all positive, positive and negative, or all negative.

Unlike DS, in Poser the neutral value is adjustable and can be anything you want. It is unfortunately not obvious how to do so, but I've taught only about 5,000 people how to do it.

You connect a Math:Subtract node to the disp map. In value_2, you enter what value you want to be neutral. It can be 0, .5, .75, 1, .341415926, etc.

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Renderosity forum reply notifications are wonky. If I read a follow-up in a thread, but I don't myself reply, then notifications no longer happen AT ALL on that thread. So if I seem to be ignoring a question, that's why. (Updated September 23, 2019)