Lighting fundamentals
- ai images
- lighting
Light is the fastest way to change how an image feels. The same subject in the same scene reads as cosy or clinical, calm or dramatic, depending on three decisions you can write directly: where the light comes from, how soft it is, and what time of day it is. Adjectives like “cosy” tell the model how the picture should feel; light decisions tell it what to render.
Three dials
- Direction — where the light sits relative to the subject. Front light fills and flattens. Side light rakes across surfaces and reveals texture. Back light (rim light) separates the subject from the background with a glowing edge. Overhead light drops shadows straight down.
- Quality — soft or hard. Soft light comes from large, diffused sources — an overcast sky, a big window, a softbox — and gives gentle transitions. Hard light comes from small, direct ones — midday sun, a bare bulb — and gives crisp, defined shadows.
- Time of day — golden hour is warm, low and glowing; blue hour is cool, even and quiet; overcast is neutral and soft; harsh noon is high-contrast and unforgiving.
A complete light note combines all three and stays with one source. “Soft window light from the left, late afternoon” is a light decision. “Beautiful dramatic lighting everywhere” is a wish.
Weak prompt
a portrait of a baker in a bakery, nice warm lighting, cinematic
Stronger prompt
Eye-level portrait of a baker, soft window light from the left (direction), diffused through a large window (quality), golden late-afternoon warmth (time), gentle shadows falling to the right
Why the stronger one works
- “Warm” and “cinematic” describe a feeling; direction, quality and time describe what to render.
- One source means one set of shadows — the scene stays physically coherent.
- When the mood is off you change one dial: the direction, the quality or the time.
A bad example
Ask: “A cosy reading nook, amazing lighting.”
“Amazing” decides nothing, and with no direction the model may light the scene from everywhere at once — flat, shadowless, and not cosy at all.
A better example
Ask: “A reading nook with one soft lamp glowing low from the right, warm amber light pooling over a wool blanket, deep quiet shadows on the left.”
One source, one quality, one colour. The shadows are as deliberate as the light.
Why it works
Light is the most physical part of an image: it comes from somewhere, falls in one direction, and casts its own shadows. Generative systems render those consequences faithfully when you name the source — and the diffusion process settles highlights and shadows in the same passes that decide everything else. That makes every light word a renderable claim: one you can add, remove and compare in isolation.
Practice
Set the light
A café wants a photo-style image of a steaming mug of cocoa on a wooden table for its evening menu. The owner keeps saying it should feel “cosy” — which, as written, is a feeling rather than an instruction.
Fill the three light slots — direction, quality and time of day — so the mood comes from the light instead of from adjectives.
A strong example (self-assessment — not machine-graded)
Direction: low light from the right, pooling across the wooden table and falling on the mug. Quality: soft and diffused — the glow of a shaded table lamp with gentle transitions and no hard edges. Time and colour: evening, warm amber, deep soft shadows stretching to the left.
Hint
Adjectives describe the goal — the slots describe what to render. “Cosy” is the outcome, not the instruction.
One source, one direction. Light “from everywhere” renders as no light at all.
Why this is the answer
The three light dials turn “make it cosy” into renderable decisions: a low lamp on one side, a soft diffused source, evening warmth. Because each dial is separate, you can fix a wrong mood by changing one of them — swap the amber for cool daylight and the same scene reads as a crisp morning. Adjectives leave the model guessing; light slots leave it nothing to guess.
Transfer
- Portraits: soft light from a window at roughly 45 degrees is the reliable, flattering default.
- Products: soft, diffused light shows form; hard light shows drama — pick one on purpose.
- Mood: golden hour reads warm and nostalgic; blue hour reads calm and cool; overcast reads neutral and honest.
- Debugging: if the mood is off, change one dial — direction, quality or time — and regenerate.
Key takeaways
- Light has three dials: direction, quality and time of day.
- Soft light flatters and forgives; hard light dramatises and defines.
- Write the light, not the feeling — “cosy” is an outcome, not an instruction.
Next
Next: Colour and mood — palettes and atmosphere, the other half of how a scene makes you feel. The generative AI entry covers how these systems build an image from words.