“Subsurface Scattering” is by far the most common concept thrown at beginner artists when they are learning how to render skin.

I want to give a clear explanation as to what the term actually means and how it applies to paintings.

And by the end of this article, you can impress your friends with your newfound knowledge and sound really fancy when you say the words “subsurface scattering” in conversation. 🙂

What the heck does ‘subsurface scattering’ mean?

The term ‘subsurface scattering’ might seem daunting but if we break it up based on each word, then it will be much easier to understand.

‘Sub’ means ‘just under’…

‘Surface’ just refers to the outside layer of something…

and of course, ‘scattering’ means ‘going different ways’.

If you put these meanings together, subsurface scattering simply describes how light scatters just under the surface of something. That’s it!

Well actually, that’s not it…but it’s all we need to start. 😉

What kinds of objects have subsurface scattering?

For light to scatter under the surface of an object, the object itself has to be ‘translucent’ and not ‘opaque’.

Opaque objects allow light to pass through whereas translucent objects allow only some light to pass through.

This bit of light that enters translucent objects is what bounces within its surface and exits in a scattered and haphazard manner.

What happens to light in subsurface scattering?

When light enters a translucent object, it typically picks up the colour of whatever it is passing through.

We often see subsurface scattering in skin and other living elements. And the majority of living things need blood to survive. So the light shines through the blood and becomes red.

NOTE: For the examples below, I showed the light rays coming from the left hand side and exiting to the right to make the image simple, but in actuality, the light source is behind the object and the light rays are coming towards the camera

For eg. in the picture above, the orange light shines through the skin and becomes shifted towards the reds as it picks up the colour of the blood.

Orange is close to reds on the colour strip so it’s easy for the warm orange light to transition into the reds. This is why the colours become so rich and intense.

Now what would happen if we take the same orange light as before and shine it through white bar soap?

The orange light is shining through the white soap is becoming ….even more orange?

WHAT EXACTLY IS HAPPENING???

When light bounces through an object, it actually loses energy as it keeps moving back and forth. As the light loses energy, it shifts towards the warms which is the oranges and reds.

In the picture above, there is no colour influence from the soap since it is white, so the change in colour of the light is only from it losing energy and becoming warmer.

So when painting subsurface scattering, there are two principles to keep in mind:

• the colour of the light picks up the colour of the object it passes through
• the colour of the light becomes warmer as it loses energy

Both are happening at the same time!

Why should I use subsurface scattering in my art?

Subsurface scattering has a way of making a painting come alive.

Mostly because we see it in our daily lives, whenever we look at a person’s face or pick up that juicy mango or look at the sunlight shining through the leaves.

We see it all around us even though we may not be aware of it. Adding subsurface scattering then helps bring a sense of believability and life to your painting.

Subsurface scattering is most evident where light meets shadow or in the shadows if the light passes entirely through the object. So if you want your art to feel real and alive, add a bit of a subsurface glow to important elements in your scene and watch the magic happen.

In conclusion…

Subsurface scattering is when light enters a translucent object, bounces around inside and exits after picking up the colours of the object.

Use it in your paintings to breathe life into it and add believability.