New LED street lighting on Hillsborough Street

If you’ve driven down Hillsborough Street at night within the past week or so, you may have noticed some new lighting. What makes this lighting noteworthy is that it is LED (right), as opposed to fluorescent or the more common sodium vapor lamps (left). 

But before we dive into why this is important, let’s take a look at the history of municipal lighting of streets, buildings, and sidewalks at night. 

Before There Was Electric Lighting 

Gas Lamp post (with fluorescent source) at Christ Church

Gas powered lamps first appeared on Fayetteville Street in the late 1850s, and increased in popularity after the Civil War. As far as I know, there are only two local remnants of this era: the converted post in front of Christ Church (above) and an iron stub on the corner of Hargett and Bloodworth Streets (below). 

A remnant of the gas lamp era

Above is a cross section of lighting types: mercury vapor (flickering/dim light), fluorescent, and sodium vapor. I’m not sure of the age of this post or the one at Christ Church, but it’s likely they both date back to the late 1800s or turn of the century. All the rest were mostly gone by the 1920s. 

Trivia: The gas powered lamp has been the logo of Goodnight, Raleigh! for nearly two years. 

Electric Powered Lamps Emerge

Image credit: NC Office of Archives and History, State Archives

Fluorescent and Mercury Vapor, Sometime Later

Mercury Vapor lighting on Fayetteville Street, 1965. Image credit: Raleigh Boy

The mid part of the century saw new lighting options: flourescent and mercury vapor. Mercury vapor is the type of lighting used on Fayetteville Street in the image above. Although it put out a mostly acceptable color temperature, it has many disadvantages including the degradation of intensity and brightness over time in addition to health and environmental concerns. 

Fluorescent lighting emits an attractive shade of white and is more efficient than incandescent, but faces other challenges. The light diffuses rapidly, making it inefficient to cover large areas. It was never widely adopted for street lighting, but is widely in use in other applications such as lighting parking lots and buildings. 

Enter The Dark Ages (Sodium Vapor)

Snow on Moore Square reveals the light traveling upward

 In the 1970s sodium vapor lighting made its way across urban landscapes across the country. Although sodium vapor  wasn’t particularly appealing in the type of light emitted, it was more efficient than other alternatives. The problem with sodium vapor lighting isn’t just that it emits a very warm color (likened to ‘prison-yard orange’ by a reader) but something much worse: light pollution. It’s no secret that the further away from civilization you are, the more stars there are visible to the naked eye at night. This is caused by man-made light traveling upward. It’s pretty easy to see photo above: light emanating upward from the lamps causes halos to form as light is reflected back from falling snow. 

Thick clouds reflecting the orange glow

All of this light shooting upwards casts an orange glow over the city, and reduces visibility to the heavens. You can see this on a much larger scale with the above image. With stationary heavy clouds overhead, the assortment of colors from the lights below are partially absorbed and partially reflected. The resulting color is shows bits of purple, red, yellow, and orange. While it may occasionally make for an interesting picture or phenomena in the night sky, this is the exception rather than the rule. 

The worst offender: low pressure sodium. Nearly impossible to compensate for.

More frequently, this is what we’re used to– a nasty shade of orange. As someone who relies exclusively on ambient night lighting for photography, I can’t emphasize enough how inadequate and unattractive sodium vapor light is. In fact, it’s frequently the reason I chose to convert some images to black and white. Sure, I think black and white imagery is attractive and in some cases adds a more ‘artistic’ look. However, I’d rather display in full color. I’d rather give a more complete representation of a scene than a pretty one, and sodium vapor often makes this difficult to do without being distracting. 

Range from 2500K to 3500K

There are ways to compensate both in camera and post-production, but only so much. Most digital SLRs allow you to manually set the color temperature (in Kelvin) used during exposure. Although this can help, in many cases the orange cast is simply too dominant and the other colors of the spectrum simply cannot be included in the dynamic range in the resulting image. Above, you can see the range from 2500K (the lowest camera setting) to 3500K. 

Color temperatures of common lighting sources

Many photo editing applications allow you to adjust color temperature as well as the saturation levels of specific colors, but it’s not enough. Colors on the other side of the spectrum (cooler colors) will be heavily distorted and give an image an artificial look. Frustrating (or perhaps something a bit more vulgar) is typically the sentiment when trying to get a good color photo illuminated only by sodium vapor. 

The Future: LED (Light Emitting Diode)

Municipal deck stairwell, 2007. The tree here is now but a stump.

Two years ago, the City of Raleigh teamed up with Cree to convert the Avery C. Upchurch Municipal parking deck to LED lighting. The stairwell above shows the contrast of the two lighting sources in the deck. The camera attempted to to equalize the sodium vapor light when determining the appropriate color temperature, resulting in the light from the deck to appear blue. (Sadly, the last time I was there, only a stump remains of the tree pictured above). 

LED on the upper level and one lamp post, sodium vapor everywhere else

This does highlight one shortcoming of LED-based lighting. Although it is a pretty bright white, it tilts on the cooler (blue) side of the color spectrum, which isn’t always attractive. The difference is that it’s a much smaller tilt in that direction. As more research and investment is made into this type of light source, we will eventually see more neutral shades of white. The advantage is that a replacement of the system won’t be necessary – it’s a matter of replacing the LEDs as the burn out. 

Why is This Important?

Although I will readily admit my interest in lighting is mostly due to increasing the appeal of the night time environment, there are larger reasons why it’s important for Raleigh to continue on the path of light enlightenment: 

• Light pollution – LEDs project light downward, which in turn creates less light pollution.
• Energy effciency – Even with a (for now) higher initial investment cost, the cost of maintenance and energy is less than alternatives.
• Environment – LEDs last significantly longer than other types of light sources (up to 50 times longer than incandescent), thus creating less waste in landfills.
• Safety – According to LED City, “74 percent of the respondents [those who use the Raleigh municipal deck] surveyed after the LED lighting was installed felt that safety in the garage was significantly enhanced”

How To Get Involved

LED in artistic applications

This Tuesday (Feb 2) will see a rally at the Convention Center to promote LED in municipal applications, coinciding with the U.S. Department of Energy hosting a Lighting Research and Design Workshop in the same location. Raleigh was chosen as the location due in large part to the strides made in converting lighting systems to LED. Cree, the local LED manufacturer is located in Durham and has contributed to a number of projects in the area. 

Let’s hope for the sake of a pretty night landscape the movement from sodium vapor to LED lighting systems accelerates.