Discover Lighting!

HID lamps are the “big bruisers” of the lamp family. When one needs copious amounts of light projected over long distances, HID gets the call. They are inherently a point source, therefore, those copious quantities can also be focused for accurate placement of the light.

The first practical HID lamp was demonstrated around 1901 although it would be 33 years until these lamps started looking and performing like the lamps we use today. This first HID lamp used a mercury arc to produce light so guess what this lamp was called? Right! An arc lamp… just kidding…it was called a Mercury lamp. This lamp type spawned several offspring, the details of whom will be described shortly. First, let’s see how and why these lamps operate.

HID lamps produce light yet a different way from the previous two lamp types. HID light is produced directly from the arc itself. Due to the high pressure under which these types operate, the arc becomes extremely intense (hint: don’t look directly at one of these lamps while they’re operating). This arc is relatively short (at least compared to a fluorescent lamp) and therefore it is considered a point source. Sometimes we don’t want a point source (don’t ask!) so some types have a coating on the inside surface of the outer bulb to diffuse the light. Some coatings are phosphor-based so they can also change the color of the light along with diffusing it.

These lamps vary in wattage from 39 – 1500 watts. Quite a range! Check them out here. They have life ratings from 6,000 – 24,000 hours, with some special types exceeding 24,000 hours. The color of light produced varies greatly, depending on the type. CRI ranges from 20 – 90 with color temperatures from 3000K to 6000K (more on this later).

Since these sources use an arc, what piece of auxiliary equipment do they need? You guessed it – a ballast. These ballasts are quite robust and heavy. Those that must handle them on a regular basis do not require membership at the local fitness center!

HID lamps, like everything else in life, have advantages and disadvantages. On the upside, they are a compact source of lots of lumens, they operate in almost any environment (not as finicky as fluorescents about temperature), and are available in a wide array of wattages to cover a variety of mounting heights and target distances.

On the downside, they have a warmup time of several minutes before they emit their rated light output, they have limited dimming capability, color can vary significantly over life, HID systems are relatively expensive, and when they are turned off, they cannot be restarted for several minutes (they need to cool down first).