Does your art look flat even though the drawing is right? Lighting in illustration fixes that: pick one clear light source, then shape every form and shadow around it.
This guide is part of our wider series on illustration techniques.
| Item | Value |
|---|---|
| Key light | Main source, positioned just off-camera |
| Fill light | Placed around 60-90 degrees from the key |
| Rim light | Sits behind the subject, edge highlight |
| Terminator | The edge where light transitions into shadow |
| Reflected light (Proko value scale) | Value 4, the lighter shadow value |
| Core shadow (Proko value scale) | Value 1-2, the darker shadow value |
Figures come from Proko’s lesson notes and Creative Bloq’s lighting guide. They can change, so check the sources before you rely on them.
Why lighting creates drama and depth
Many artists draw clean outlines and then lose the volume when they shade. Proko’s notes put it this way: “Many students draw beautiful outlines but flatten their forms with incorrect shading.”
Light is what tells the viewer which way a surface faces. It also tells them how far away it is, and what mood the scene carries.
Drama comes from contrast and from a clear decision. Depth comes from how light turns around forms and falls off across the picture.
Before you pick a colour, ask three questions:
- Where is the main light coming from?
- How hard or how soft is it?
- What colour is it, and what colour is the shadow?
The parts of light and shadow
Lit forms can show the following zones, depending on their material, shape and lighting. Proko’s notes list them: the terminator is “the edge where light transitions into shadow”, and the form shadow is “the area beyond the terminator, turned away from the light source.”
The cast shadow “occurs when an object blocks light from hitting another surface.” Cast shadows and form shadows have different causes, but both belong to the shadow family.
- Halftones: light areas where the form turns away from the centre light and gets progressively darker.
- Highlight: a reflection of the light source on shiny surfaces. Matte surfaces have none.
- Reflected light: light bouncing from the environment into the shadow, lightening it slightly.
- Core shadow: the darkest part of the form shadow, usually along the terminator.
- Occlusion shadow: the darkest value in tight crevices where objects touch.
Even on smooth forms like spheres, thinking in terms of planes helps you understand how the form turns. A sphere is a good practice object because it can show many of these zones under suitable lighting.
Shading in the right order
Proko suggests a simple order. First block in the reflected light at value 4, which is your lighter shadow value. Then add the darker core shadow at values 1-2.
This keeps the shadow side unified instead of a muddle of greys. The reflected light stays lighter than the core shadow, which is what makes the form look round.
For matte surfaces, the same notes use light halftones at values 8-9, medium halftones at 6-7 and dark halftones at 4-5. If there is a clear highlight, simplify to two halftones plus the highlight as the brightest spot, value 10.
Practise this on grey spheres before you apply it to characters. When you draw figures, a loose pose from gesture drawing gives you the big forms that light can then sit on.
Key, fill and rim: a lighting setup you can borrow
Film and 3D artists use a three-light setup, and it works just as well on a blank canvas. Creative Bloq’s guide, published 7 January 2026, describes each role.
- Key light: “The key light is your main source, positioned just off‑camera, defining the primary direction and shadow character.”
- Fill light: “The fill light, placed around 60-90 degrees from the key, enhances shadows.”
- Rim light: “The rim light sits behind the subject, separating it from the background with an edge highlight.”
In a painting you do not need to place real lamps. You only need to decide where each of the three sits, then keep the fill weaker than the key so the picture keeps a clear main light.
The same guide advises keeping the fill’s power low, so it fills in the gaps and creates natural-looking contrast. A rim light can help separate a dark figure from a dark background.
Colour temperature and mood
The key light also sets the colour of the scene. According to Creative Bloq, it “establishes the shadow direction and the colour temperature of the lighting.”
A common painter’s approach is to make the light and the shadow opposite in temperature. A warm key with cooler shadows reads as sunlight, and a cool key with warmer bounce light reads as moonlight or screens.
Try changing the power, position, colour temperature and size of your lights one at a time. Creative Bloq says experimenting with these four settings teaches lighting fundamentals quickly.
When you move into colour, a digital painting workflow lets you test warm and cool versions on separate layers without redrawing.
A quick workflow for your next piece
- Thumbnail three or four value layouts with one light direction each.
- Choose the key light and mark where the terminator falls on the main forms.
- Block in the cast shadows as one flat, unified tone.
- Add reflected light, then the core shadow, then occlusion shadows in the crevices.
- Add a rim light only where it helps separate the subject from the background.
Keep each step separate. Finishing the big shadow shapes before any detail stops you from chasing small marks while the overall light still looks wrong.
Common lighting mistakes to avoid
Most lighting problems come from mixing decisions rather than from weak rendering. Check your work against this list.
- Two competing key lights, so the shadows point in different directions.
- Shadows that are as light as the lit side, which flattens the form.
- Reflected light that is brighter than the lit areas, which makes the shadow side glow.
- A rim light on every edge, which turns the subject into a cut-out.
- Cast shadows that ignore the shape of the surface they fall on.
A useful test is to squint at the piece or reduce it to greyscale. If the main shapes still read as light, halftone and shadow, the value structure may be clear; check that colour choices preserve that clarity.
Lighting also guides the eye. Put your strongest contrast, where the brightest light meets the darkest shadow, around the focal point, and keep the rest quieter so the viewer knows where to look first.
Frequently asked questions
What is the terminator in drawing?
Show answer
It is the edge where light transitions into shadow on a form, according to Proko’s lesson notes.
What is the difference between form shadow and cast shadow?
Show answer
A form shadow sits on the side of an object turned away from the light. A cast shadow happens when an object blocks light from reaching another surface.
What does a rim light do?
Show answer
It sits behind the subject and adds an edge highlight that separates the subject from the background.
Do I need a fill light in a painting?
Show answer
Not always. A fill light enhances shadows, and keeping it low in power keeps the contrast natural.
