How to use Subsurface Scattering in Principled BSDF

Question

The Subsurface Scattering in Principled BSDF is a bit confusing:

• Where can I find some material presets?
• What is the difference between Scattering Color and Radius?

Answer 1

Subsurface amount

• Use it to scale Scattering depth down to realistic values
• When set to 0, scattering is disabled

Values of around 0.01 are normal, since you're scaling from meters to milimeters

Subsurface Radius (aka Scatter Color)

• Visible on edges and translucent parts (like ears and fingers)
• Connect an RGB node or a texture. This is a good place for a subdermal map
• The RGB values represent how deep light penetrates in meters

Scale the radius down using the Subsurface slider

Subsurface Color

• Visible on opaque parts and in shadows
• Use the same image/color you used for Base color to avoid color mixing

Subsurface Anisotropy

• Bias between forward-scattering rays and backward-scattering rays
• Realistic skin has an anisotropy around 0.8

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Example of Subsurface Scattering setup

• Stanford Dragon, 15 centimeters
• Marble material set from the reference chart below

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Subsurface Scattering values

• Drag the chart into Blender's image editor and use color picker to select colors
• For SSS to work correctly, your model needs to be in real world scale.

_{^{Source chart from Pixar. Original paper here}}.

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Sources
_{^{Link - Henrik Wann Jensen, Stephen R. Marschner, Marc Levoy and Pat Hanrahan: "A Practical Model for Subsurface Light Transport". SIGGRAPH'2001.
An Introduction To Real-Time Subsurface Scattering, Stanford Dragon - Stanford University Computer Graphics Laboratory, Subsurface - Arnold Renderer, Subsurface - Substance Painter, Subsurface - Renderman}}