Vision, Viewing And Lighting

The lighting requirements for regular office work and viewing a video display and the visual tasks presented are in fact opposite.

Modern offices have generally been designed to achieve overall good working conditions for employees dealing with ordinary paper work. Even so, illumination of North American offices is generally overdone, often to a point close to visual discomfort on the premise that "more is better!"

Some building owners or their rental agents are going as far as advertising that their premises offer 100 foot/candles at desk level of lighting -- something that has been accepted as a normal office requirement.

Let's compare that with some recommended light levels from the "Human Factors Reference for Facility Designers" published by Lockheed Missile:

Task Condition Light Level
(Foot/candles) Type of
Lighting
Very difficult and prolonged visual tasks with objects of low brightness contrast. High speed and extreme accuracy required. 100 or more Supplementary. Special Fixtures such as desk.
Small detail, fair contrast, close work, speed not essential. 50 or more Supplementary
Prolonged reading, assembly, general office, ordinary bench or laboratory work. 25 or more Local lighting and ceiling fixtures directly overhead.
Occasional reading. Washrooms, power plants, waiting rooms and kitchens. 10 or more General lighting
No detail vision necessary. Stairways or supply houses. 5 or more General or supplementary lighting.

Task Condition	Light Level (Foot/candles)	Type of Lighting
Very difficult and prolonged visual tasks with objects of low brightness contrast. High speed and extreme accuracy required.	100 or more	Supplementary. Special Fixtures such as desk.
Small detail, fair contrast, close work, speed not essential.	50 or more	Supplementary
Prolonged reading, assembly, general office, ordinary bench or laboratory work.	25 or more	Local lighting and ceiling fixtures directly overhead.
Occasional reading. Washrooms, power plants, waiting rooms and kitchens.	10 or more	General lighting
No detail vision necessary. Stairways or supply houses.	5 or more	General or supplementary lighting.

The ever more frequent introduction of CRT display terminals in traditional offices has led at times to impossible workplace problems.

Lighting becomes unsuitable for the new and complex visual tasks of CRT terminals. Situations where the operator has simply switched the lightts off and works in almost total darkness are not unusual. Switching the room light off (rarely possible in North America as most buildings have "floor switches") is of course not a solution, since the operator then cannot read the document which hopefully is placed close to the terminal, and he/she can scarcely see the engravings on the keyboard. What is more -- when the operator task calls for both work at a terminal as well as regular/clerical desk and paper work, the ambient illumination in the room should be kept at a level allowing for comfortable readability of written and printed documents.