What is a Spectroradiometer?

Jessica Reed
Jessica Reed
Woman doing a handstand with a computer
Woman doing a handstand with a computer

A spectroradiometer is a device designed to measure the wavelengths of individual colors of light. The visible light spectrum is made up of six colors, each formed by a different wavelength which determines its color. The spectroradiometer measures spectral power distributions given off by a light source. This simply means it separates each wavelength, or color of light, it detects and then takes an individual reading for each color. The results tell how strong each color of light is and how strong the light source is as a whole.

The term spectroradiometer is closely related to radiometry. Radiometry is the study of electromagnetic radiation. Light is one form of electromagnetic radiation and thus included in the scientific field of radiometry. Both radiometry and spectroradiometry are used by astronomers to study objects in space. Spectroradiometry can help scientists measure visible light waves which, in turn, help determine factors such as temperature based on the color of the light.

Aside from its use in astronomy, the spectroradiometer is also useful for measuring the quality of light from common, household light bulbs. A manufacturer needs to test the light bulbs and label them according to how much power they produce, and what types of light they give off. Different bulbs cover different ranges of the color spectrum and can give off light that appears warm or cool in color. What the device is measuring when it tests the light bulbs is how much power it detects on each color, or wavelength, coming from the light. We see all the colors mixed together, but the spectroradiometer can break them into individual bands of color for a more accurate reading.

Light bulbs aren't the only items the spectroradiometer works on. It also helps when calibrating computer monitors or television screens. Specific types of displays, such as a CRT display or an LCD display, often require calibration to find the right color balance and settings. To ensure that the monitors give off the proper amount of color either individually or in relation to each other, spectroradiometers take a reading of what is referred to as CIE color.

CIE color readings are then compared to the ideal reading of the TV. Once this comparison is made, it is simple to determine what color adjustments to make. After adjusting, another reading may be taken to ensure that the color is balanced and at the desired setting. If not, the new reading can point out what adjustments are still required.

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Discussion Comments


@Iluviaporos - The color of light you want to use in a reef aquarium really depends on what you want to grow and the shape of the tank.

If you've got a really shallow tank, you can get away with not so much blue light, but if you have a deep one, you'll need a high percentage of blue lights.

That's because blue/white light will penetrate much deeper into the water than yellow light.

If you are planning on having a deep reef tank though, you should really research a lot about the different kinds of light and how to measure them, before you set it up. They can be very expensive, and of course, the fish and corals are dependent on you getting it all right.


@pastanaga - It makes sense that a mixture of yellow and blue lights is closer to a natural spectrum, as that is the combination usually recommended for reef aquariums.

Although, in that case, they often say you should use small spectrophotometers to check how well your bulbs are doing, and whether you have the light at a good point. Even if your lights come set up already, it's a good idea to have one, I think because they usually don't just burn out, they get gradually darker as the time goes by, and might change color.

Since light is so essential to a reef, it pays to keep an eye on what kind of light your reef is receiving.


It doesn't seem like it's all that important what color light is produced by a light bulb, but it can make a huge difference to the look of a room. Yellow light is much warmer and to a certain extent, easier on the eyes than blue light. Blue or white light, on the other hand, is "colder" and can be harsher, but is brighter and puts things into better contrast.

When you are selecting the lights you want to put in an area, it's best to mix them up, in my opinion, so you have a wider spectrum of light, which is closer to what natural light is anyway.

That will also bring out the natural colors in your decor as well.

You probably won't need spectrometers for this though, as they generally label bulbs with their color now.

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