LIGHTFAIR 2001 Pre-Conference Workshop Description

In this seminar, you will learn: 1. An explanation of the photometric measurement process and its relation to the accuracy and reliability of photometric reports. 2. An in-depth understanding of photometric reports, including IESNA LM-63, CIBSE TM14, and EULUMDAT file formats. 3. A non-technical analysis of lighting design software algorithms, with particular emphasis on understanding how they work and how to use them properly to produce photometrically accurate predictions and physically correct renderings. Part I –Photometric Laboratories 1.1. Photometric Units 1.1.1. What Is Light? “Let me give light, but let me not be light.” Wm. Shakespeare The Merchant of Venice Act V, Scene I Light is electromagnetic energy, which includes radio waves, microwaves, infrared, visible, ultraviolet, X-rays and gamma rays. We can think of it as subatomic particles (called photons) flowing through space in all directions. Each photon has a certain energy that is determined by its wavelength. More usefully, we can think of light as the flow of electromagnetic energy – so many photons per second, similar in principle to the flow of electrical current. For visible light, this flow is measured in lumens. Ref: IESNA Lighting Handbook, Ninth Edition, Chapter 2. ANSI/IES RP-16-95, Nomenclature and Definitions for Illuminating Engineering. Photometry and Radiometry: A Tour Guide, www.helios32.com (Resources). 1.1.2. Illuminance The illuminance of a surface is the amount of light incident upon the surface, divided by the area of the surface. It is measured in either footcandles (lumens per square foot) or lux (lumens per square meter). We can measure illuminance with an incident light meter (FIG. 1). The photosensor absorbs light incident upon its surface and converts into an electrical current. Ref: IESNA Lighting Handbook, Ninth Edition, Chapter 2. ANSI/IES RP-16-95, Nomenclature and Definitions for Illuminating Engineering.