Candelas Lumens and Lux By Owen F Ransen

Candelas Lumens and Lux is a very brief introduction to the basic ideas and math of illumination engineering.

The book, which costs \$19.99, has 146 pages, half of which are diagrams. Below is a PDF file which contains the first two pages of each chapter in the book:

I decided to use tons of graphics because it is the more immediate way of explaining the subject. We are talking about light after all! Here is a sample of the graphical explanations in the book:

When you get to the end of the book you will understand the difference between "Candelas, Lumens and Lux", and have a clear idea of other important lighting concepts.

The book can be used as a self study course on lighting terminology and calculations, as well as the basis for a class course.

Chapter 1 is about the three main units used in lighting specification and calculation: Candles (luminous intensity), Lumens (flux, or quantity of light) and Lux (illumination on a surface).

Chapter 2 is about Luminance, (very roughly the appearance, "brightness", of objects), including the luminaires themselves (and their light emitting surfaces) as well as objects and worksurfaces illuminated by them:

Chapter 3 shows you how to read photometric diagrams, both C-Gamma and VH diagrams:

Chapter 4 explains the basics of internal lighting, and how to calculate the number of luminaires of a given type for a certain sized room using the Room Index and Lumen Method:

Chapter 5 explains how a Sollner diagram and luminaire glare are related, and how to interpret the UGR (Unified Glare Rating) number and table. A simplified Sollner diagram is shown below along with the polar diagram for the same luminaire...

... and its usefulness as well as its limitations are explained in the book.

Road lighting is covered in some detail in chapter 6. For example why do most luminaires designed for roads have wide wings in their photometric diagram? Look at this photometric diagram:

(A clue: the red "wings" shoot light up and down the road, and the blue curve shoots light...where?)

And how do you interpret a road lighting utilization diagram? Here's one:

A clue: We are looking at the luminaire "side on" the left half is the side-walk, the right half is the..?

The book has complete answers, and more:

"Candelas Lumens and Lux" covers the subject for visible light, using concepts for photometry rather than for radiometry. Radiometry covers the whole electromagnetic spectrum, whereas photometry considers only the visible spectrum. There is an brief description of the spectra of the 'standard' eye and the luminaire and how they relate to each other in Chapter 7.

Here is one of the illustrations from that chapter:

Here is a partial index of the book:

The answers to the quiz questions in the book are here.

\$19.99

There is now a poster of the book available! Ideal for school, colleges and universities:

The poster is 28" by 20" (71 x 51cm)

(c) 2017
Contact me if you have any questions about or suggestions for the book.