For decades the better light bulbs were the cheaper light bulbs because they all had similar durability, appearance and performance. These old-school bulbs worked on a simple premise: connect electricity from the wall through to the filament causing it to super-heat to the point of glowing red hot, thereby emitting light. Because the filaments were glowing hot they gave off light with a full range of colors. Furthermore, because the filament had some weight to it the thermal mass continued to glow hot even between the rapid short interruptions in power inherent with alternating-current (“A/C”) electrical power. It is the continued output of light between A/C power cycles is known as persistence.
The light was good. Life was good.
How are LEDs different?
LEDs have two core characteristics that require enormous engineering and manufacturing resources to overcome. It’s the quality of the solutions to these two characteristics that really separate poor bulbs from superior bulbs.
The first characteristic is that unlike old incandescent bulbs, LEDs have no persistence. An absence of persistence means that when power is interrupted many times each second as a function of A/C electrical power, the LEDs flicker between on and off states unless manufacturers implement solutions to overcome this.
The second core limitation is that common LEDs don’t emit a full range of colors like incandescent bulbs do. In fact, quite unlike anything you might find in nature, LEDs tend to only emit a narrow range of color, often in the blue/violet spectrum.
It’s the solutions to these two characteristics that separate poor LED bulbs from superior bulbs – and it’s why quality now matters more than ever.
Overcoming limitations of LEDs
As discussed above, we know that connecting LEDs directly to A/C power will result in flicker because of the rapid interruptions of power inherent to A/C electricity and the lack of persistence. To overcome flicker, manufacturers must include a “driver”, usually in the base of LED bulbs. Drivers are essentially a small circuit board populated with various electronic components and in most cases include a capacitor to store small amounts of electricity. The role of the driver is to modify the power supplied from your power outlet into something suitable for the LEDs inside the bulb. This conversion usually includes a reduction in voltage, but more importantly the driver is supposed to reduce or eliminate flicker by filling in momentary interruptions of power with power stored in the on-board capacitor.
An effective driver will reduce flicker to amounts comparable to an incandescent bulb (despite persistence, incandescents still do exhibit mild flicker in the form of pulsing). Some drivers are so good that they even eliminate all measurable flicker. Unfortunately, capacitors are fairly large in size and sensitive to heat (and yes, LEDs and drivers do produce more heat than you might expect) which makes fitting them, together with drivers into small bulbs extremely difficult.
Overcoming limitations of color also requires engineering know-how. For a long time LED bulbs were synonymous with a harsh blue, cold color temperature. More recently, researchers have discovered that if they cover blue LEDs with a special phosphor layer that actually absorbs some of the blue light and converts it to green, yellow and red through the process of fluorescence, then a more balance white appearance is achieved without a significant drop in efficiency. In a nutshell, this is the emergence of a white LEDs (also known as WLED) you might see advertised on the retail box of a television. Because WLEDs contain a reasonable distribution of all colors of the spectrum they appear more natural white than early LED bulbs.
Shortcomings of poor quality LED bulbs
Some of the shortcomings of LED bulbs will be visible, while others will be invisible. High frequency flicker typical of most LED bulbs is often invisible but can still contribute to symptoms for those most sensitive. Harsh flicker is usually the result of a poorly designed driver, insufficient space within the bulb for a capacitor with the driver, or simply a manufacturer trying to cut costs at the expense of user comfort. Most LED bulbs flicker at 100Hz or 120Hz. At these frequencies it’s fairly easy to identify harsh flicker by simply capturing it with a smartphone camera. Read more about capturing flicker with cameras here.
Not all manufacturers properly balance the colors of their LEDs with fluorescence or other techniques. If you’ve ever noticed how objects illuminated by poor quality LED bulbs look a bit cold, hollow or just lack the vivid color, then you’ve already seen what poor color production looks like. When colored objects don’t look right it’s because the nearby light emits insufficient energy within the specific wavelength of those colors. In other words, if the light is missing colors, or emits a low intensity of specific colors, then nearby objects will appear discolored.
Reliability is also a problem with poor quality LEDs, though with sale prices now reaching as low as $1.00 USD per bulb, a failed bulb is unlikely to cause much grief apart from taking up space in a landfill or resources at a recycling facility.
Identifying superior LED bulbs
So, how do you identify an LED bulb with good light performance? With great difficulty. Let’s break down color, flicker, durability and markings you might find on retail packaging.
Color is easiest specification to investigate because retail bulb packaging often contains helpful hints. If you’re sensitive to displays on electronics like your phone, computer or tablet, or even if you struggle with sleep at night, then you may want to avoid bulbs that emit high levels of blue light. Thankfully, manufacturers now include the Correlated Color Temperature (“CCT”) specifications on retail packaging. While not a direct measure of blue light output, it is in fact a measure of the average of all color emitted from the light source. If you select an LED bulb with a warm CCT of 2700K or lower, then the blue light output will be subtle and the bulb will instead give off higher levels of green, yellow and red light resulting in a familiar warm yellow color similar to old incandescent bulbs. Selecting a higher, colder-looking CCT such as 4000K or 5000K will result in a bulb with a harsh white or even blue appearance consistent with a supermarket or hospital. Cooler CCTs like 4000K or 5000K will invariably emit more blue light that may contribute to symptoms for those most sensitive.
Quite separate from CCT is the Color Rendering Index (“CRI”). A good CRI score of higher than 90 is usually a sign of a better LED bulb, but not always. The premise of CRI is that if colors are missing from the light produced then nearby objects will appear discolored, or have a ‘hollow’ appearance. The CRI score itself is calculated by averaging the scores of only the first eight colors of the index (R1-R8), which are a variety of unsaturated, pastel colors. This should give you a rough idea as to color performance of a bulb.
While the rest of the colors (R9-R15) aren’t included in the CRI score itself, they do still play an important role in color performance. Specifically, the strong red (R9) often scores poorly in modern LED bulbs resulting in discoloration of nearby objects containing shades of red, including skin, wood, vegetables etc.
The CRI R9-R15 colors usually track fairly closely to R1-R8. A well-performing LED bulb with a CRI of greater than 90 usually has an all-important red R9 score of 55 or better, which is very reasonable. The take-away here is that if you’re concerned with color performance, stick to bulbs with advertised CRI scores of greater than 90.
Be extremely wary of purchasing LED light bulbs without any CRI score. Marketing departments will certainly use a high CRI score to promote their products if the product does in fact have a high score. An absence of CRI scores will almost invariably mean the bulb has poor or inconsistent color performance. Be mindful of marketing departments interfering with the usefulness of the CRI if it’s listed. A CRI score “up to” provides no helpful information whatsoever. A CRI score of equal to or “greater than” is helpful as it assures purchasers a minimum level of color accuracy.
Flicker is quite problematic for those most sensitive and unfortunately isn’t properly described on retail packaging. Don’t be fooled by claims of “flicker-free when used with dimmer” as this doesn’t necessarily mean the bulb will be flicker-free. Finding a flicker-free bulb is a trial-and-error affair until Energy Star (or California) adopts specific requirements. Read more about capturing flicker with cameras here and have a look at this video for examples of what the capture may look like.
Durability typically comes down to one issue: a cheap driver. A driver with poor assembly or inappropriate components will be the weakest link in terms of a durability of an LED bulb. Drivers are composed of several electrical components of which a single failed component will result in an inconsistent or non-functional bulb. As discussed above, one of the components often included on a driver is a capacitor to help reduce flicker. Unfortunately, capacitors are particularly sensitive to the heat generated by the driver and the LED themselves. In the tight confines of a light bulb this creates design challenges for manufacturers. If the capacitor is of poor quality and the bulb of poor design, it will likely fail leaving you with either a non-functional bulb or possibly a bulb with very harsh flicker characteristics. Most people aren’t capable of tearing down a bulb to identify the quality of internal components, so best practice is avoiding bargain bin bulbs and instead opting for a more premium bulb offered by a reputable company with a good warranty period of three years or greater.
The Energy Star logo you’ve likely seen stamped onto your appliances may also be present on the LED bulb packaging. The logo stands for a lot more than efficiency. It means the bulb is compliant with the published specifications of Energy Star requirements for LED bulbs. The requirements include a minimum CRI of 80, CCT accuracy within around 1% margin of error, warranty of a minimum of three years and other requirements.
Recommendations for those most sensitive
We still recommend use of incandescent or halogen bulbs for those most sensitive. Fluorescent bulbs share many of the same trade-offs of LEDs and are therefore not recommended. Once users are comfortable with incandescent or halogen bulbs and the baseline symptoms they can expect with good lighting, they can then explore other lighting options, including LEDs. The baseline is important as without it you’ll never know if LED lighting is contributing to your symptoms.
If you’re keen to save money on energy bills, know that the the solid-state lighting industry is still evolving rapidly and surely with some government intervention, lighting quality will improve and someday may even exceed the performance of incandescent and halogen bulbs. But, we’re not there yet. Finding good lighting is still a minefield, but with some luck you’ll find LED bulbs you’re comfortable with. Have a look at our lighting section for some reviews, though exceptional bulbs are very few.
For those not sensitive, now has never been a better time to save some money on your electricity bill by switching to LED lights. The worst performing LED bulbs are now behind us by a few years. We recommend narrowing your search to bulbs carrying an Energy Star certification, as this certification should eliminate the poorest quality bulbs and bulbs that don’t reliably meet the specifications printed on the packaging. A particularly important choice is the color temperature (CCT) of the bulb. If you’re unsure, opt for 2700K bulbs for bedrooms and living rooms and a 3000K bulb for busy areas of the kitchen. Bulbs with a CCT of 4,000 or 5,000K are best suited for laundry areas Choosing the wrong color temperature will certainly result in dissatisfaction with lighting, so do your homework first.
We hope that superior lighting will one day allow us to make a single recommendation for all. But, for now we recommend you opt for high performance bulbs as you may just be looking at them for the next 20 years.
One thought on “LED vs incandescent bulbs: why quality now matters”
This is a good article, I would recommend it to friends.