---
title: "Generalized lighting vs localized lighting"
subject: "Industrial Power Distribution and Illumination"
chapter: 7
key: "semester_6/industrial_power_distribution_and_illumination:generalized-vs-localized-lighting"
source: https://www.bctengineer.com/q/semester_6/industrial_power_distribution_and_illumination/generalized-vs-localized-lighting
site: BCT Engineering
---

# Generalized lighting vs localized lighting

Industrial Power Distribution and Illumination · Chapter 7: Illumination Design Principles

- Asked in: 2072 Asoj, 4 marks
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/industrial_power_distribution_and_illumination/generalized-vs-localized-lighting
- Whole chapter: https://www.bctengineer.com/md/semester_6/industrial_power_distribution_and_illumination/chapter-7

## Question

What do you understand by generalized lighting? Explain with suitable example why localized lighting cannot be employed alone.

## Short answer

Generalized lighting supplies uniform illumination across the entire area via regularly spaced luminaires. Localized lighting alone creates high contrast, eye strain, dark gangways, shadows and safety hazards, so it must always be accompanied by a general lighting scheme to maintain acceptable background brightness.

## Answer

**Generalised (general) lighting** is a scheme in which luminaires are arranged in a regular pattern over the whole area to give a **uniform level of illumination** on the working plane, regardless of where the work is done. It lights tasks, gangways and surroundings alike.

Example: a classroom or a textile weaving shed lit by rows of LED panels/tube fittings at equal spacing to give about 300 lux everywhere.

#### Why localised lighting cannot be used alone

**Localised lighting** puts lamps close to particular work points (machine lamp on a lathe, bench lamp). If it is the only lighting:

1. **High contrast and eye fatigue:** the eye moves between a very bright task and dark surroundings and keeps re-adapting, which causes strain and headache.
2. **Safety hazard:** gangways, stairs, moving cranes and obstacles stay dark, so workers may trip or collide; finding exits in an emergency is difficult.
3. **Harsh shadows and glare:** a single nearby source throws deep shadows and may reflect off shiny work.
4. **Poor supervision and cleaning:** the general area cannot be inspected or maintained easily.
5. **Gloomy, unpleasant environment** that lowers morale and productivity.

Example: in a machine shop, a lamp on each lathe gives 1000 lux on the tool, but a worker walking between machines with no general light cannot see oil spills or moving trolleys. So local lighting is always used **with** general lighting (general-plus-local scheme), with the general level at least about one-third of the local task level.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. What is generalised lighting?
   A. Lamps placed only at machines
   B. Luminaires in a regular pattern giving uniform illumination over the whole working area
   C. Light from windows only
   D. Emergency lighting for exits
   Answer: B. General lighting gives a uniform level everywhere, independent of where the task is. (Key point: Definition of generalized lighting)

2. Why does localized lighting alone cause eye fatigue?
   A. The lamps are too dim to see anything
   B. The eye keeps re-adapting between a very bright task and a dark surrounding
   C. The lamps flicker at 50 Hz
   D. It uses too much power
   Answer: B. High contrast between task and surroundings forces constant adaptation, causing strain and headache. (Key point: Glare and eye strain)

3. In a machine shop with only lamps on lathes, what hazard arises?
   A. The lathes overheat
   B. Gangways stay dark, so workers may trip, collide with trolleys or miss spills
   C. Lamps cut the supply voltage
   D. Machines run slower
   Answer: B. Areas away from task lamps get no light, creating safety risks; hence a general-plus-local scheme is used. (Key point: Safety with local lighting only)

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