Expert: Karl Smith - 12/29/2005

Question
I am an interior design student, just finished a lighting class.  I am still confused about how to distinguish from cool and warm light sources.  I know fluorescent is cool, however, it doesn't look cool to me, or warm for that matter.  Maybe it just comes with experience.  Also, what does a lighting designer do exactly.

thank you

cheryl

Answer
There are three different questions here.

1. How do I tell the visual colour of light?
2. How do I tell the colour content of light?

To understand them you need to understand how the eye / brain works.

3. What does a lighting designer do?

Usually correct obvious errors in design made by interior designers and architects.

1. The visual colour of light is the ambient affect created by light, with fluorescents the are several colour options, cool white, white and warm white are the main ones although there are many others dependant upon the application.

For example cool white tends to be used in clinical environments to depict cleanliness, white in industrial environments for light without comfort to create and environment for work and warm white in offices to create comfort. However its not that simple as each specific environment should be designed with regard to window sizes, reflective qualities of surfaces, volume of space, specific tasks (localised or area wide)

2. The colour content of light is the degree Kelvin of the spectrum or constituent light prevalent in a lamp. The quality of surfaces, materials and colours is directly linked to the light that falls upon it, if a red material has a blue content (invisible in the white colour of light) light put on it the eye cannot see its true colour but will rather see it as another colour. Hence meat counters in supermarkets using high red content lamps which look white but make the meat look deeper red (hence to our minds fresher).

3. Lighting designers face an up hill struggle to get other specifiers to understand that a 3 week course in lighting cannot possibly outweigh years of knowledge. I have been a lighting designer for 20 years and still do not know everything I want to. I have specified in the region of 2,200 different lamps (types) in this time and designed 180 new fittings with optics that do not exist on any other fitting in production. Additionally 9 of the luminaries I have designed are in mass production, but I never ever produce formulaic designs, every project is considered on its own merits. It is imperative to fulfil the client's requirements, most of the work I do is fix designs made by people who have limited knowledge, and under CDM (Construction Design Management) in the UK they have made criminal design choices as they are not professional lighting designers.