LED Match Making – The Value of Photometric Analysis

By Charlie Szoradi | Independence LED Lighting  

Many commercial building owners and operators may have more light than they need in certain areas and less light than they need in other areas. When considering an LED retrofit, do not just buy new lights for the energy savings, but take the time to get the right type of lights to meet your business operating needs. Photometrics Analysis is a great way to “see” a plan and elevations of the current foot candle light levels and the potential to increase or decrease levels where needed.

As an example, for a national auto service chain, Monro Muffler and Breaks, one of the managers at a Connecticut location spoke about the need for more light in the service bays to show customers what needed to be fixed on their cars. The managers also spoke about a brighter more appealing overall look to their service centers to attract more customers. For a top BMW dealership in Virginia, the requests included improved light quality to showcase the vehicles. They wanted customers to be able to see the vehicles with brighter light and with color temperatures to more closely match how the vehicles appear outside in daylight. Since color temperature is measured in Kelvin and Kelvin impacts output in lumens, the lumens impact the foot candles. A photometric analysis helps shape the optimal lighting solution. In another example, an Anheuser Bush beer distributor, in Pennsylvania, with over 300,000 sq. ft. wanted to ensure 30 foot candles at the floor as well as on the storage racks. They wanted to be able to load the trucks more quickly with fork lift truck operators clearly seeing the palette labels under brighter light. In this case, the photometric analysis included both floor plans and elevations. The results of the study drove the inclusion of reflector systems where appropriate on the LED high Bay light fixtures. In each of these examples the right amount of light played a role in improving the operations of the business not just a reduced energy bill.

To better understand photometric analysis, here are some highlights from Wiki.

Photometry is the science of the measurement of light, in terms of its perceived brightness to the human eye.It is distinct from radiometry, which is the science of measurement of radiant energy (including light) in terms of absolute power. In modern photometry, the radiant power at each wavelength is weighted by a luminosity function that models human brightness sensitivity. Typically, this weighting function is the photopic sensitivity function, although the scotopic function or other functions may also be applied in the same way.

The human eye is not equally sensitive to all wavelengths of visible light. Photometry attempts to account for this by weighing the measured power at each wavelength with a factor that represents how sensitive the eye is at that wavelength. The standardized model of the eye’s response to light as a function of wavelength is given by the luminosity function. The eye has different responses as a function of wavelength when it is adapted to light conditions (photopic vision) and dark conditions (scotopic vision). Photometry is typically based on the eye’s photopic response, and so photometric measurements may not accurately indicate the perceived brightness of sources in dim lighting conditions where colors are not discernible, such as under just moonlight or starlight. Photopic vision is characteristic of the eye’s response at luminance levels over three candela per square metre. Scotopic vision occurs below 2 × 10−5 cd/m2. Mesopic vision occurs between these limits and is not well characterized for spectral response.

Based on this description above, the net of the photometry science is that it is more complicated than most business owners or operators care to learn. So, the tip below is as simple as working with the right people to navigate the complexity.

Top Tip on LED Light Matching with Photometrics:
Choose a commercial LED lighting manufacturer or solutions provider that has the software to run photometric analysis on your facility before making a major LED purchase. This gives you the power to review your options with objective data laid out in easy to review, multi-color floor plans and elevations.

ILL_Charlie-SzoradAbout the Author
Charlie Szoradi is the Chairman and CEO of Independence LED Lighting, an award-winning US LED Manufacturer. He has taken a leadership role in sustainability and lighting for more than 20 years, dating back to his Master’s Thesis at the University of Pennsylvania on “Energy Intelligence” in 1993. He has multiple patents and is a sought after speaker for both industry and academic events. Szoradi is available by e-mail at Charlie@IndependenceLED.com.