Lighting Technology Comparisons

Not so long ago, light bulbs were light bulbs. Today you can choose from incandescent, halogen, fluorescent, LED or discharge lamps. It’s hard to believe that it took nearly 60 years to perfect the incandescent light bulb which can only convert 5% of energy into light.

So how do we select which light technology is best for any given application? Efficacy, colour performance and controllability are key visual factors for choosing a light source. Price also is a determining factor that includes initial cost, operating cost and service life cost. Secondary factors include technology material environmental compatibility, lamp operating ambient temperatures and performance issues.

Determining Factors

Luminous efficacy

Efficacy ratings vary significantly among different technologies and applications. A light bulb’s efficiency is a measure of emitted light (lumens) divided by power it draws (watts). A bulb that is 100 percent efficient at converting energy into light would have an efficacy of 683 lumens per watt (lm/W).  To put this in context, a 60-to 100-watt incandescent bulb has an efficacy of 15 lm/W, an equivalent CFL has an efficacy of 73 lm/W, and current LED-based replacement bulbs on the market range from 150 lm/W for the latest LED area luminaires.

Colour performance

To predict accurate colour performance, Colour Rendering Index (CRI) is a quantitative measure of the ability of a light source to faithfully reproduce the colour of an object when compared to the colour it looks like under natural daylight. The higher the CRI, the more accurate the colour rendition.

Because the incandescent lamp is an artificial light source, it has a very broad spectrum with even illumination. Halogen is similar, however CFL and LED have gaps in the emission spectrum. Its lower CRIs mean that some wavelengths have zero emissions, while others are skewed abnormally high. These characteristics give rise to the typically blue appearance of LED lights, and the blue-to-green appearance of CFLs.

Life-time cost

Consider how much a lighting source costs to purchase and operate over the course of a system’s lifetime and then weigh it against the service life and luminous efficacy. Incandescent bulbs being made of a tungsten wire dangling toward gravity are only rated at 2000 hours while LED’s whilst a lot more expensive expect to last 100,000 hours. This makes LEDs cheaper over 10 years.

What’s best?

Each application must be weighed on its merits to determine the cost benefits tailored to your specific needs. However, all data seems to favour LED technology, partly thanks to its high-performance diodes that provide excellent luminous efficacy and a maintenance-free life. It provides lower CO2 emissions for the same light output as the conventional bulb, whilst providing better resilience to harsh industrial environmental conditions such as extreme temperatures and explosive atmospheres.