Archive for August, 2014

In a recent article published in Architectural SSL on the topic of blue light content of LEDs, I attempted to present the discussion of blue light from the perspective of those raising concerns about blue light hazards against known and practical objective knowledge on the topic. The article covered the gambit of concerns, from retinal damage concerns to melatonin levels in occupants, from both sides of the argument, as there are those who dismiss this as a non-issue out of hand. The article also forwarded two conclusive suggestions. First: The research on this specific topic, as it relates specifically to LED light sources, is a little thin. Second: For those concerned about blue light content, selecting LEDs of a lower CCT and higher CRI delivered the lowest blue light content. Whether or not this is the best choice for visual acuity was not the subject of the article, nor was it suggested as the best solution overall. There is a great deal of research supporting the concept of high CCT light for enhancing human visual performance. Much of this was completed under light sources other than LEDs, so there is no caveat included that states anywhere that blue light content of LEDs is at acceptable levels, or of no concern. (more…)

After reviewing a range of different metering choices in actual use, I compiled a summary of findings, as well as my own personal subjective ratings of features and overall utility as a lighting professional. This chart is the collection of all findings in a simple comparison table for those who find this useful (like me): (more…)

This is the Lighting Passport Flagship set. Includes case and accessories in a neat package.

This is the Lighting Passport Flagship set. Includes case and accessories in a neat package.

I first saw this device at Light+Build Frankfurt last fall. I was impressed enough to find one added to my collection of tools. The Asensetek Lighting Passport is a unique product in several ways. First, it is essentially a meter head (where the cost is), coupled to an iOS or Android device that does all the computational and display work. The lighting head has a nifty slide action receptor cover, so there is nothing to come off or get lost in a bag or pocket. The measurement range is as broad as any of the other spectrometers tested here, plus some. Not only does it produce the expected spectral power distribution, CRI, CCT, CIE 1931 and 1976 coordinates and illumunance in lux and Fc, it also delivers CQS values. (more…)

We have now entered the modern era, where meters are available with a dazzling array of features, at a fraction of the cost once commanded. In this case, the UPRtek MK350S, available also in a lesser featured, and lower cost MK350N version, produces amazingly beautiful results with little pain in the wallet or the head from learning to use it. You may find this also sold under other brand names, such as AIBC, or sold through outlets such as Allied and Ikan. I first saw the MK350S at Light+Build in Frankfurt. A customer of mine also saw them, and was so impressed, he purchased one and has allowed me some time to play with it and in preparation of building up a test lab for his company. (more…)

Okay, so while this is not of the same caliber, or as new and cool as the spectrometers, and could be considered an obsolete product, since it is no longer made – but, there are enough of these meters around in used condition, and they have been in use for so long, that finding one with the right attachments is not a serious challenge. So why bother? To start, the basic meter frame sold new for over $1,5000, with attachments to produce various readings. I found one example on ebay, sold from a test lab that was closing, that included several useful sensor heads. (more…)

To compliment a standard light meter, which does a fine job collecting illuminance information, I sought a low cost solution to evaluation of color data, specifically CCT, spectral power distribution and CRI. My goal was to find a product under $2,000, that could be calibrated, that would deliver me color information simply and without a large amount of special technical effort. I found that in the Mightex CCD Spectrometer. At a base price under $1,700, it fit the budget nicely. Of course I added a few accessories to it, and paid them to calibrate the meter with a fiber optic mounted cosine sensor, which increased the total invoice to a touch beyond the $2,000 target… However, in the end, I found the results to be exactly what I was looking for – almost. (more…)

When it came to setting up a lab with a proper precision meter for collecting and evaluating color (CCT) and color quality (CRI), as well as measuring transmission, luminance, radiance, irradiance, and illuminance of light sources and fixtures, I chose the Orb Optronix SP-100. This was done in partnership with a customer, for whom we set up a complete lab with goniometer we built for the customer, for testing their ongoing products as part of a design services agreement. In time as the customer grew in their own capacity, the entire rig, along with the data processing protocol we developed over several years, was transferred to the customers own facility, where staff was trained to complete their own tests in-house, where this is still in use today. (more…)

This is going to be a quick one. First of all, no matter what other meters one might own, the basic illuminance meter, with its readout in Lux or Fc remains an essential. You pull it out, press a button, get a number. The issue is with the latest generation of LED fixtures and retrofit lamps. They present a somewhat skewed spectral balance that can cause issues with older meters. For example, my trusty old (very very old) Minolta Color Meter II shows all LED sources as being roughly 200 CCT cooler than they actually are, sometimes, sometimes not. My other old trusty bag filler is a Minolta T-1H, which is great under daylight and tungsten sources, but not so good under LEDs, where  readings are off about 12% most of the time, and when exposed to LEDs with any flicker in them – the meter has a hard time finding a reading to settle on. I also have a Testo 540 digital ligth meter, which is an excellent in-the-pocket device, as it is very slim and includes a cover for the light sensor. At a cost of under $140, they are hard to beat for a simple tag-along meter for general illuminance measurement. (more…)

Introduction

Light meters are an essential tool for anyone involved in the lighting profession. The human eye lies to us with its unique capacity to invisibly correct for brightness variations, while the brain fills in missing pieces and compensates for color variations. For professionals, it is important to see through this biological variability to understand what we are actually looking at. One might ask why, if observers are compensating so readily, is it necessary to have objective understanding? These are the five reasons I feel having sufficient light metering is a critical tool for lighting professionals: (more…)