what a shame noone answers on those basics…
shame on ppl here…
the higher your subdevision level is the higher your detail is
problem: your pc won work with 12 SD level and 1000000000 polies…
so you should think like this: what will be my model and what will be texture.
try to get you medium detail with regular SD levels. do as many SD as a normal 3d program can handle. in my case on a mac pro it is 3 million polies in cinema 4D.
the rest i do via textures.
so what u need to get detail is a texture… a normal map or displacement map.
so the way u go is via HD-geometry. you sculpt all details like skin pores or wrinkles into hd-geometry. u can work with 12 million polies and even more. but you sculpt only on a little circle because not whole model is covered with this huge polie density. so you have also 3 million polies. but only for a nose till exempel. then u go to the eye then to the ear and so on. at the end you covered whole model with hd geometry u safe teh HD information under a displacement or normal map. and all those detail u gonna safe as map.
if your model is not a human. its more sth more complexe and bigger like a plane then you shold try to subdivide it in subtools
no subtool should have more polies than 3 mio.
hope that helped. the only limit yu have in zbrush is your hrdware so try to arrange with your hardware to get best results.
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