my advise it to keep the 1:10 ratio between blur radius and samples (default 2:19), otherwise soft shadows tend to become "blodgy" (whatever the word is, irregular, with dark and light spots).

So when I crank up the radius to 20, samples is set to 200. And soft shadows don't come at 100%, so shadow intensity has to be reduced too (say 50%, 70% max). Min Bias means that small details from displacement maps will not generate shadowing, only larger details will. This is a softening effect too: softer, more ambient / environmental light has a larger Min Bias.

One does not need IDL only to get better shadows, just master the shadow-settings. Shadows are important in portrait photography. Like landscaping is "painting with light", so is portraying "painting with shadows".

All the best.

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Usually I'm wrong. But to be effective and efficient, I don't need to be correct or accurate.

visit www.aRtBeeWeb.nl (works) or Missing Manuals (tutorials & reviews) - both need an update though