Lighting Guide
Photometric Data Guide
Everything buyers need to read a luminaire datasheet: photometric curves, IES files, UGR glare ratings, IP and IK protection ratings — explained in plain language.
What Is a Photometric Curve?
A photometric curve (polar diagram) shows the luminous intensity of a fixture in candela (cd) at every angle. The curve tells you:
- How narrow or wide the beam is — a tight curve means a spot optic, a broad curve means a flood.
- Where the light actually goes — up, down or sideways — which matters for wall washing, display and anti-glare design.
- The beam angle — the angle where intensity falls to 50% of the peak (FWHM).
- Efficiency — the ratio of total emitted lumens to the lamp lumens.
| Term | Meaning |
|---|---|
| Candela (cd) | Luminous intensity in a given direction |
| Lumen (lm) | Total visible light output of the fixture |
| Lux / fc | Illuminance on a surface (lm per m² / per ft²) |
| Beam angle | Angle at 50% of peak intensity (FWHM) |
| IES / LDT file | Standard photometric data format for design software |
| UGR | Unified Glare Rating — discomfort glare scale 0–30 |
How to read it in three steps: ① find the peak intensity angle (usually straight down for downlights), ② check the 50% point to read the beam angle, ③ compare the curve shape — narrow and tall = spot, wide and flat = flood.
UGR — Unified Glare Rating
UGR measures discomfort glare on a 0–30 scale (lower is better). It is calculated from the luminaire's luminance, its position in the field of view and the room surfaces.
| UGR | Application |
|---|---|
| ≤ 13 | Drawing offices, video conferencing |
| ≤ 16 | Offices, classrooms, screen work |
| ≤ 19 | General offices, retail (EN 12464-1) |
| ≤ 22 | Industrial and utility areas |
| ≤ 25 | Circulation and storage |
Reduce glare with deep-shielded optics, honeycomb louvers, higher cut-off angles and indirect lighting. See the interactive UGR guide.
IP & IK Protection Ratings
IP — Ingress Protection
First digit: solids (0–6). Second digit: liquids (0–8).
| IP20 | Indoor, dry areas (standard) |
| IP44 | Splash-proof, bathrooms (some zones) |
| IP65 | Dust-tight + water jets, outdoor |
| IP67 | Temporary immersion, wet locations |
IK — Impact Protection
IK rating (00–10) measures resistance to mechanical impact in joules.
| IK05 | 0.7 J — standard interior |
| IK07 | 2 J — corridor / public areas |
| IK08 | 5 J — vandal-resistant |
| IK10 | 20 J — heavy vandalism / prisons |
FAQs
Photometric Data Questions
Common questions about IES files, UGR, IP and IK.
What is photometric data in lighting?
It describes how a luminaire distributes light — intensity per direction, beam angle, total lumens and efficiency — usually published as curves or IES/LDT files.
What is an IES file used for?
IES files let lighting design software (DIALux, AGi32, Relux) simulate real light distribution in 3D, so you can predict lux levels before installation.
What is the difference between IP and IK ratings?
IP covers dust and water ingress; IK covers mechanical impact. A fixture can be IP65 (weatherproof) but low IK (fragile) — specify both for the environment.
What UGR should I specify for an office?
EN 12464-1 recommends UGR ≤ 19 for general office tasks and UGR ≤ 16 for screen-based work. Lower UGR means less discomfort glare.
Do you provide IES/LDT files for your fixtures?
Yes. We supply IES and LDT photometric files for our track lights and downlights, plus full photometric test reports. Request them with your project details and we will share the files.
Need Photometric Files or a Lighting Design?
Ask for IES/LDT files and a free photometric layout — our engineers will model your space and confirm lux levels.