Light sources and terminology: a quick guide to modern lighting concepts

Lighting terminology can seem complex at first. Understanding the basics — lumens, kelvins, CRI, socket types and light distribution — makes choosing the right light source much easier.

1. Lumens (lm): actual brightness

Lumens indicate how much light a bulb produces. For LED bulbs, lumens matter more than watts.

2. Color temperature (Kelvin, K)

  • 2700K–3000K – warm, cozy

  • 3500K–4000K – neutral white

  • 5000K+ – cool, bluish

3. CRI (Color Rendering Index): color accuracy

  • CRI 80+ – general lighting

  • CRI 90+ – kitchens, bathrooms

  • CRI 95+ – professional environments

4. Socket types: E27, E14, GU10, G9

The bulb’s socket must match the fixture.

5. Light distribution

Affected by:

  • diffusers

  • reflectors

  • lenses

  • micro‑prismatic diffusers

6. Dimmability

LED bulbs may be:

  • dimmable

  • 3‑step dimmable

  • non‑dimmable

7. Lifespan

LED bulbs typically last 15 000–50 000 hours.

8. Lighting concepts

Good lighting includes:

  • ambient lighting

  • task lighting

  • accent lighting

Summary

Knowing the terminology helps you choose the right light source and design functional, comfortable lighting.