Luminance vs. Illuminance: What’s the Difference?

When it comes to the appearance of color, you cannot underestimate the importance of lighting. Yet, lighting can be confusing, as much of the terminology sounds similar but has vastly different meanings. For example, two of the most widely used terms — luminance and illuminance — can be easily misunderstood and mixed up. Since lighting is an essential component of color, we’ll discuss the difference between luminance and illuminance below.

What Is Luminance? 

The definition of luminance is the amount of light emitted, passing through or reflected from a surface. Think of a lamp shining in a dark room — luminance would describe the amount of the light passing through the lightbulb.

Luminance is often used interchangeably with the term brightness. However, when it comes to luminance vs. brightness, these descriptions are not interchangeable. Luminance is a quantifiable, measurable characteristic. Whereas brightness cannot be objectively measured — it can only be perceived. We recognize that a light source is bright or dim, making brightness the visual sensation by which we become aware of differences in luminance.

When it comes to color decisions for your business, luminance can also describe a certain color’s perceived brightness. 

How to Measure Luminance

Luminance is measured in luminance intensity, which is a measure of how bright a beam of light in a particular direction is. There are a variety of units used to express luminance. The International System of Units uses candela per meter square (cd/m2), while in the U.S., the most common luminance unit of measurement is the foot-lambert (fL).

If you wish to determine color luminance, you can use a spectrophotometer. This device provides three-dimensional numeric values, or L*a*b color space, precisely defining an object’s color. The “L” in L*a*b stands for lightness value. This ranges from 100 — which is pure lightness — to -100 — which is pure darkness.

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What Is Illuminance? 

Illuminance describes the amount of light falling onto or illuminating a given surface area. You illuminate something by shining or projecting light toward it. Luminance is the amount of light reflected off a surface being illuminated — this is how you convert luminance to illuminance.

How to Measure Illuminance

Illuminance calculates the total amount of light a source puts out. This luminous flux is measured in lumen per meter square, or lux.

Learn More About Color Measurement Devices by HunterLab

Lighting is an essential factor to consider when measuring the color of something. The same colors can be viewed in a variety of ways under different lighting conditions. At HunterLab, we take the guesswork out of color matching with sophisticated color measurement technology.

Our first-class color-matching spectrophotometers ensure that you receive accurate color measurements. By understanding a color’s luminance value and other color-scale values, these advanced machines are the right tools for the job if you want to get the correct color data.

Contact HunterLab today to learn more about measuring and working with color and lighting.
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