notes

emission & geometry

• collimation: parallel vs diffuse rays
• incidence angle: direction of arrival
• source - subject distance: governs intensity and coverage
• source shape: outline controlling distribution
• source count: number of discrete emitters
• layering: arrangement of multiple sources/zones
• gradient: centre-to-edge falloff sharpness

intensity & quality

• intensity: brightness affecting highlights
• bloom: internal optical/sensor glow
• scatter: diffusion by particles or surfaces

spectral

• color: correlated color temperature and tint

optics

• refractive shaping: lens curvature/refractive index converging/diverging rays
• focal length: physical distance between lens and sensor for focus at infinity

geometry at capture

• ray density: number of rays per area at sensor
• focus state: convergence accuracy on sensor plane

• inverse-square law: intensity ∝ 1 / distance²
• long focal lengths: require greater sensor - lens distance -> longer barrels; barrels block oblique rays, narrowing directionality structurally
• out of focus: blur circles and sharpness loss
• low ray density: dim or oblique light reduces brightness despite correct focus
• distant extended source: small subtended angle -> point-like appearance, angular collapse
• diffuse light: larger area increases softness; distance still controls falloff

• natural sunlight/window: large relative source size, consistent direction, stable color (except golden hour/foliage), shaped by environment, single dominant source
• artificial studio pitfalls: multiple unmotivated sources, unnatural placements (e.g. under-chin), excessive uniformity, mismatched scale/placement
• background lighting: use gradients and controlled color; black = intense/mysterious/elegant; white = airy/clean/high-key; seamless materials; tape edges regular
• reference practice: study photography, CGI art, and film stills for lighting ideas