Photometry, Colorimetry & Spectroradiometry -
a Training Course on the Science of Light Measurement
Lighting is an exciting and rapidly developing area - LEDs and solid state lighting promise not only energy efficiency but also design flexibility. Yet LED specifications are often mistrusted. Together with measurement service specialists Photometric Testing, Pro-Lite holds regular one day training courses in photometry and light measurement that help you to understand LED and lighting specifications, to seperate truth from fiction and show you how to measure and express the output of your products. An optional practical session is offered on the second day where delegates can gain hands-on experience with the latest, state-of-the-art measurement equipment.
Why is the subject of LED specifications so hotly disputed? LEDs are mass produced and there is a significant variation in the brightness and colour of the LEDs as they come off the production line. Manufacturers test and group LEDs by brightness and colour (a process called "binning"). However, in general, LEDs are tested under very idealised conditions - a short flash of current is passed and the LED does not have chance to achieve a steady state temperature. When LEDs are clustered into a luminaire or other product, the LED temperature rises above the nominal 25°C and the light output falls. At the 70-80°C operating temperature typical of many light fittings, the LED flux (lumen output) has dropped by 30% compared to the initial level (some people refer to this as "hot lumens" versus "cold lumens"). At the same time, the correlated colour temperature (CCT) of the LEDs rises and the colour rendering (CRI) also changes. Unlike traditional lamps, you have to test the assembled luminaire with LEDs fitted as a finished product - simply estimating luminaire performance based on the output of the component LEDs will be very misleading. Our course will explain both the theory and practice of how to measure the output of LEDs and luminaires.
The following comments about our training course were kindly provided by staff at retail lighting specialists Microlights Ltd. Thanks to Anna Enright (New Product Project Manager) and Philip Sharpe (Marketing Manager):
"Microlights pride ourselves on understanding customer needs. [Pro-Lite] understood our training requirements and educated us so that we can pass technical information on to our customers in a clear and concise way"
"Technical information, provided in a non-technical way"
"Detailed, tailored training - yet easy to understand"
"Training that was expert, smart and focussed to our needs"
Our training course has been developed over 7 years and has previously been presented to in excess of 750 delegates. Our trainers are noted for their ability to communicate complex subjects in a clear, easily understood way and we have consistently been awarded top marks for the quality of our teaching. Our course will empower all of these working with the next generation of ultra efficient lighting to understand the important optical metrics and communicate clearly and effectively within their own supply chain and with customers. The course will be of value to both technical and as well as marketing staff working with displays and lighting.
Basic Concepts - Light & the Human Visual System:
Light and the electromagnetic spectrum
Mesopic & scotopic vision
Basic Concepts - the Optical Properties of Materials:
Diffuse reflectance & transmittance
Lambert's cosine law
Specular reflectance & transmittance
BRDF and scatterometry
The inverse squared & cosine rules
Photometric field (near-field versus far-field)
Converting between units
Colour vision and tristimulus theory
CIE colour spaces
Integrating Sphere Flux Measurements:
Integrating sphere theory
Choosing the correct size sphere
Calibrating an integrating sphere
Correcting sample absorption
Goniophotometry & Standard Photometric Data:
Standard photometric data (IES & EULUMDAT)
Absolute versus relative photometric data
Errors with filter photometers
Spectral power distributions
Colour rendering (CRI)
Colour quality scale (CQS)
LEDs & Solid State Lighting - the Measurement Challenges:
Temperature effects on LED output
LED binning & the effect on brightness & colour
LED phosphors & the effect on colour
BS EN 13032-1-2:2004 & 13032-3:2007
Photobiological Safety of Lamps & Lighting:
Standards - BS EN 62471:2008
The Artificial Optical Radiation Hazard Directive
How to measure and calcluate exposure levels
Measuring flashing light sources
Calculating luminous exposure and effective intensity
Visual Alert Devices & BS EN 54-23:201