LESSON 15 · VALUE & LIGHT

There are two kinds of shadow and they behave completely differently. A form shadow happens because a surface turned away from the light; a cast shadow happens because something blocked the light. Once you can tell them apart, and once you stop letting the shadow family leak into the light family, your forms start looking solid instead of smudged.

SOFTWARE

Finish first: L14

• A desk lamp and a white ball, an egg, or an orange
• A cardboard box and a cylinder - a tin or a candle
• A blank 2000x1500 canvas and your five saved value swatches

WATCH

Marco Bucci — Ten minutes that will change how you see light permanently. Watch it twice, and build the rest of this lesson around it.

Proko — Optional only. The 2012 Proko video is still a clean, correct primer on form shading. This 2026 Proko video (Ben Eblen) is a genuinely stronger, modern treatment of inventing light on stylised characters and is worth adding or swapping in - individual video embed only, never the channel.

Proko — Treats the shadow as a designed shape rather than an accident - the idea that turns correct shading into good shading.

THE LESSON

Every value in a lit scene belongs to one of two groups. The light family is everything the light source can reach. The shadow family is everything it cannot. The border between them is called the terminator, and it is the single most informative line in any painting.

This is the rule that carries the whole module: nothing in the shadow family may ever be as light as anything in the light family. Not the brightest reflected light, not the shiniest bounce off the tabletop. If the two families overlap in value the form dissolves - the viewer can no longer tell which parts face the light, and everything goes soft.

Practically, you decide the value budget before you render. Give the light family values 1 to 2 on your five-step scale and the shadow family values 4 to 5, leaving value 3 as the halftone at the edge of the turn. Then paint inside those limits and refuse to break them. Marco Bucci's video is ten minutes on exactly this point, which is why it is worth watching twice.

Put a white ball under a single desk lamp and you can see every term you will ever need. Closest to the lamp is the highlight - not the object's colour at all, but a reflection of the light source itself. Around it is the light, the broad area facing the lamp. As the surface curves away you get the halftones, a gradual darkening that still belongs to the light family.

Then the surface turns past ninety degrees to the light and stops receiving it. That transition is the terminator, and just inside it sits the core shadow - usually the darkest part of the object itself, because it is the region that neither receives direct light nor much bounced light.

Further round, inside the shadow, the value often lifts slightly. That is reflected light, bouncing off the table onto the underside of the ball. Beginners paint it far too bright because it looks dramatic. It is not dramatic in life - it is a small lift within the shadow family, and it stays there.

Finally, where the ball touches the table there is a very dark, tight band. That is the occlusion shadow, the one place almost no light of any kind reaches. It is often the darkest value in the picture, and it is what makes an object sit on a surface instead of floating above it.

A form shadow exists because the surface itself turned away from the light. Nothing is blocking anything; the geometry simply rotated past the point where light can land.

Its defining feature is the softness of its edge, and that softness is not a style choice - it is set by how fast the surface turns. A sphere turns gradually, so its terminator is a soft, wide gradient. A cube turns instantly at ninety degrees, so its terminator is a hard line on the corner. A cylinder is soft around the wall and hard at the ends. Airbrush a soft terminator onto a box and the box becomes a pillow; put a hard terminator on a sphere and it becomes a paper cutout.

The shape and softness of a form shadow therefore describes the form. When you are unsure how soft to make it, ask how fast the surface is turning at that exact point.

A cast shadow exists because an object stood in the way and stopped light reaching something else. It behaves in three ways a form shadow does not.

First, its edge is sharpest where the object meets the surface and softens as it travels away - the shadow of a chair leg is crisp at the floor and blurred at the far end. Second, its shape describes two things at once: the silhouette of the object casting it, and the terrain it lands on. A cast shadow crossing a staircase breaks and steps; one crossing a curved wall bends. That is why cast shadows are so useful - they describe surfaces you have barely drawn. Third, it is darkest next to the object and lightens with distance.

The size of the light source controls all of it. A small, distant, hard source - the sun, a bare bulb - gives crisp cast shadows with defined edges. A big, close, soft source - an overcast sky, light through a curtain, a window - gives shadows so diffuse they barely have an edge at all. Decide what kind of light you are drawing before you draw a single shadow, because that decision sets every edge in the painting.

Work in shapes instead. Decide where your light is - draw an arrow in the corner of the canvas and keep it visible for the whole session. Then select the entire shadow family as one flat shape with the Lasso and fill it with a single value from your swatches. Do it wrong, undo, do it again. Only once the flat shadow shape reads correctly at thumbnail size do you allow yourself to render inside it: the core shadow, then the reflected light, then the occlusion.

Two habits keep this clean. Put the cast shadow on its own layer so you can move, reshape or soften it without touching the object. And use lock transparent pixels on the object layer so everything you paint stays inside the silhouette you established.

PRACTICE · 40 MIN

1. Set a single desk lamp to one side of a sphere, a box and a cylinder on a plain surface. Turn the room lights off so there is one dominant source.
2. Draw an arrow in the corner of your canvas showing the light direction. Leave it there for the whole exercise.
3. For each object, lasso the entire shadow family as one flat shape and fill it with value 4. Do not render anything yet.
4. Zoom out to thumbnail size. If the three shadow shapes do not immediately tell you where the light is, redo them.
5. Now render inside the shadow shapes only: core shadow at value 5 just inside the terminator, a small lift for reflected light, and a hard occlusion shadow where each object meets the surface.
6. Render the light family: value 1 nearest the lamp, halftones stepping down to value 3 as the surface turns.
7. Handle the terminators correctly - soft on the sphere, hard on the box corner, soft along the cylinder wall but hard at its rim.
8. Add cast shadows on a separate layer. Keep each one crisp at the contact point and soften the far end.
9. Label the finished sheet with text: highlight, light, halftone, terminator, core shadow, reflected light, cast shadow, occlusion.

Done when: Three rendered forms with correctly separated light and shadow families, correct terminator hardness on each, and eight labelled parts.

Download these and work along with the lesson.

CHECK YOURSELF

Answer out loud first, then open each one to compare.