How Bright is Bright?

In recent years, the traditional light bulbs we all grew up with have moved to more sophisticated types with different terminology.

Most people are accustomed to selecting light bulbs for home use based on “watts”. But what does it all mean?

First, let’s discuss different types of light bulbs.

Though Edison is usually credited with the invention of the light bulb, the famous American inventor wasn't the only one who contributed to the development of this revolutionary technology. There were others who researched and demonstrated electric batteries, lamps, and earlier versions of light bulbs.

On January 27, 1880, Thomas Edison filed his patent for the light bulb. Lewis Howard Latimer improved upon Edison's original design, adding a more durable filament made of carbon. He developed and patented a process for efficiently manufacturing the carbon filament making light bulbs more affordable and practical. Eventually, tungsten became the most common filament.

Traditional light bulbs are “incandescent”, which means “glowing” or “white with heat” and “intensely bright” (Dictionary.com).

When electrical current makes contact with the base of the bulb, the electricity heats the tungsten filament housed inside, creating “incandescence” or light produced by heat.As the filament continues to burn, particles fly off the filament and when there are no more particles to burn, the light bulb burns out and must be replaced. Typically, this takes place 800-1,200 hours into the life of an incandescent light bulb.

Basically, incandescence is fire and fire produces more than just light. It also produces heat. In fact, incandescent light bulbs produce 90 percent heat and 10 percent light. If you have ever touched a lit incandescent bulb, you have experienced the 90/10 heat-to-light ratio. Ouch!

Let’s clarify lamps and bulbs. Generally, most people call the fixture that traditional bulbs screw into a “lamp”. But technically, it’s a fixture (in the lighting business we call it a “luminaire”). The thing that attaches to a luminaire is a lamp. So, bulbs are actually lamps and lamps are actually fixtures. Not too confusing, is it?

Improvements to the traditional lamps include CFL and Halogen. CFL is a “compact fluorescent light”. Compact fluorescent lamps (CFL bulbs) are a twist (pun intended) on traditional fluorescent technology. CFLs screw into a fixture socket but have a spiral design – as opposed to the traditional long flourescet tube – making it "compact" and suitable as a replacement for traditional incandescent lamps.

Halogen lamps are incandescent lamps consisting of a tungsten filament sealed into a compact transparent envelope that is filled with a mixture of an inert gas and a small amount of a halogen element such as iodine or bromine.

The combination of the halogen gas and the tungsten filament produces a halogen cycle chemical reaction which redeposits evaporated tungsten back to the filament, increasing its life. This allows the filament to operate more brightly than a standard incandescent lamp of similar power and operating life.

Halogen lamps are brighter than their original incandescent predecessors. Halogen headlamps are used in many automobiles. Halogen floodlights are used in outdoor lighting systems, especially large recreational areas like football and baseball fields. Tungsten halogen is used in the majority of theatrical and studio (film and television) fixtures because of the longer lifespan and the increased brightness of these lamps.

And then there’s LED. LED lamps have come a long way in the last few years.

An LED lamp produces light using one or more light-emitting diodes (LEDs). LED lamps have a lifespan many times longer than equivalent incandescent lamps and are significantly more efficient than most fluorescent lamps.

Like incandescent lamps (and unlike most fluorescent lamps), LEDs come to full brightness immediately with no warm-up delay. Frequent switching on and off does not reduce life expectancy as with fluorescent lighting.

Landscape lighting, depending upon when and by whom it was installed, may use incandescent, halogen, or LED lamps. At Moonglow Lightscaping we only use LED, because of the long life of the lamps and the reduced energy consumption required.

Now that we’re familiar with types of lamps, let’s introduce some new terms.

Most people consider watts to be equivalent to brightness, and select lamps based on that criterion. In that sense, a 60W lamp is brighter than a 25W lamp, and it certainly appears to be that way.

A “watt” measures how much electricity is being used by an item. If a package for a light bulb says the bulb uses 60 watts, or 60W, it means that that bulb will consume 60 watts of electrical power. This does not indicate how bright a light bulb is, however. Lumens are used to initially measure “brightness”.

A lumen measures the amount of light that comes from a lamp. A standard 40W lamp is equal to 400+ lumens, which represents the brightness of the lamp. Typically, the higher the wattage the higher the lumens, and the more the light output.

Exactly how bright is 100 lumens? Since watts measure energy output and lumens measure brightness, the conversion can be tricky.

Energy-efficient lamps such as LED or CFL use less wattage than a standard incandescent, halogen, or fluorescent lamp. But even though an LED lamp uses less wattage, it will have more lumens than a standard bulb. For example, a 4W LED bulb is 220+ lumens which is equivalent to the same number of lumens found in a standard 25W bulb.

A standard bulb uses more energy to produce the same number of lumens as an LED bulb. With LED, the same brightness is achieved with less wattage or energy, and LED is thus more efficient, which saves energy and consequently can save the consumer money.

There are a number of lumens to watts conversion charts available on the internet.

But wait! There’s more!

We also must consider the temperature of a lamp. This isn’t about how hot or cool the lamp is when you touch it. Instead, color temperature describes the warmness or coolness of the appearance of the light that comes from a lamp. Color temperature is measured in degrees of Kelvin on a scale of 1,000 to 10,000; for consumers in commercial and residential lighting the range is typically between 2000K and 6500K. In landscape lighting, we usually stay within the 2000K to 3000K range, and 2700K is the most common lamp temperature we use.

Essentially, the lower the Kelvin scale number, the warmer the light - and conversely, the higher the number the cooler the light. Warmer light in this sense means more toward a soft yellow, and cooler leans in the other direction toward a very cold blue. Daylight is about 6500K.

In the landscape lighting industry, a 7W 3000K lamp is bright and cool. We most commonly use lamps that are 5W and 2700K and these provide a cozy, warm light that’s perfect for outdoor lighting. Some people prefer soft and warm, some people would rather have a brighter cooler look.

We use higher lumens and cooler temperatures for situations where security is the most important factor. In any case, we work with the customer to determine exactly the mix that works best for them.

And there you have it. Now you can figure out how bright is bright.

In another post, we’ll talk about “beam spread”. Stay tuned!