If you mean real realism (like a photograph) done with Poser: Forget about it (at least an easy way simply isn't possible).

In my experience, the way to go to get "realism" is individual for each image, for each scene.
A girl with hair that looks like wax or rops won't look real. A face with teeth made out of wood can't look real. A teeny face with skin scaned from a 30 year old woman can't look real. Reflections without something like a skydome can't work (only few materials do not reflect at all - even skin-color is influenced by the colors around).
The list with such things is very long.

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