Shape it with light.

A plaster bust, a grey ball and a chrome ball in a small studio. Move the lights around the subject, change their type, size and colour, measure them with a light meter and watch a physically based render refine itself. From the inverse square law to Rembrandt, HDRIs and False Color.

STAGE

3D Viewport

Meter points

Drag a light to move it around the bust · MMB orbit · Wheel zoom

Render

Reference

LMBSelect / drag a lightWheelDistance of the selected lightMMBOrbitHHide / showCtrlZUndo

KEY IDEAS

Direction, size, colour, amount

Every light is described by where it comes from, how big it looks from the subject, what colour it is and how much there is. The rest is balance between lights.

Inverse square law: At twice the distance a small light gives a quarter of the light: 2 stops less.
Apparent size: A light that looks big from the subject gives soft shadows; a small or distant one gives hard shadows.
Key, fill, rim: The key draws the shape, the fill opens the shadows, the rim separates the subject from the background.
Lighting ratio: The light on the lit cheek divided by the light on the shadow cheek. 2:1 = 1 stop, 4:1 = 2 stops, 8:1 = 3 stops.
Colour temperature: In kelvin: low values are warm (candles, tungsten), high values are cool (shade, blue sky).
Middle grey: A surface that reflects 18% of the light. Exposure is measured in stops above or below it.

BACK IN BLENDER

The same lights in Blender

Blender has the same four light types, the same World and the same Color Management. The lab renders them with a fast progressive renderer instead of Cycles or Eevee, with a simplified set.

Add › Light: Point, Sun, Spot or Area. Object Data Properties (the light bulb tab) has Color, Power (W) or Strength (W/m² for the Sun), and Radius, Angle or Size, which make shadows soft.
Aim a light with a Track To constraint pointing at the subject, as the lab does, and move it around freely.
For colour temperature, use a Blackbody node on the light (in the light's node tree) or pick the colour by eye.
World Properties › Surface: Background colour or an Environment Texture with an HDRI. Rotate it with a Mapping node.
Render Properties › Color Management: View Transform (Standard, AgX, False Color) and Exposure.
A grey ball and a chrome ball next to the subject are the standard way to check light and reflections, in CG and on film sets.