While looking at some of the many light-emitting devices, such as televisions, LCDs, or light bulbs, you've probably noticed they're not all the same. Some are dim, while others are very bright, and often times you can even adjust the brightness or luminance settings. Display manufacturers use different units and specifications such as nits, lumens, luminance, brightness, or light output to describe their product's light-emitting properties, so it's essential to understand what they're talking about before making a purchasing decision.

Light Concepts

Before we compare light measuring units, it's essential to understand some concepts:

• Illuminance: The amount of light that hits a surface. (how illuminated that surface is)
• Luminance: The perceived amount of light emitted from an object. Luminance is also referred to as brightness.
• Lumen: The total amount of visible light emitted from a light source. It's the unit to measure luminous flux.
• Luminous Flux (Lux): The amount of light emitted in every direction and measured in lumens.
• Luminous intensity: Amount of visible light emitted from a source in a particular direction per unit solid angle. The candela is the SI unit for luminous intensity.
• Candela: The unit measurement for light intensity. A candela measures the amount of luminance intensity from any point in a single direction.

The light from one candle is roughly one candela. Some of the highest candela ratings are seen in spotlights or lasers since most of its light is concentrated in one direction.

Learn more: Types of LCD

Light Measurement Units

We can measure light based on the brightness seen by the human eye. The most common units used to measure light are Lumen, Lux and Candela.

Light International System of Units (SI)

Nits

What are Nits? Nits (or NITS) are a measure of luminance, meaning it measures how much light an object emits. The term nit comes from the Latin word nitere, which means "to shine". The nit doesn't officially belong to the International System of Units (SI) or any other measurement system. 

One NIT is equivalent to one Candela per square meter. Not only do they represent the same type of quantity, but they’re also equivalent units.

Average consumer LCD displays have a luminance of 200 to 350 nits. For LCD displays used outside, 400-700 nits are minimum for use in daylight conditions, and at least 1000 nits to view in bright, direct sunlight. We sell Sunlight Readable displays and IPS displays designed with high brightness LED backlights for outdoor applications.

Lumens

The lumen (lm) is the unit of measurement for luminous flux in the International System of Units (SI). Luminous flux is a measurement of how much light is emitted by a source measured in lumens. Lumens are commonly used in light bulb product specifications to describe how bright the light is. The light output from a projector is also commonly measured in lumens.

Lumens vs candela

Lumens describe total light output in all directions and candela describes light output or intensity from a specific point in a single direction.

Nits vs Lumens

Although both the Nit and the Lumen are units used to measure light output, the key distinction between the two is that the Nit measures luminance or brightness of an object, and lumens measure how much light is being emitted.

Candela vs Nits

1 Candela equals 1 Nit. Other than the name, there is no difference between Candela and Nits.

Luminance

Luminance (Lv) measures the amount of light emitted from, reflected, or passed through an object. Luminance is measured in candela per square meter (cd/m²).

Although there are various units of measurement for luminance, including the Nit (nt) and the foot-lambert (fl), the International System of Units (SI) specifies the candela/square meter (cd/m²) as the measuring unit for luminance.

Related: Image Burn-in

FAQs

What is luminance measured in?

Candela per square meter (cd/m²).

Whats the difference between Luminous flux and luminous intensity?

Luminous flux measures the total amount of light emitted by a light source across its whole angular spectrum. In contrast, luminous intensity measures light emitted by a light source in a given direction.

Whats the difference between Luminance and Illuminance?

Luminance is the amount of light emitted from the source and illuminance is the amount of light that hits a surface.

Is brightness the same as luminance?

Brightness is not the same as luminance and does not have a quantitative measure. Brightness is a perception and is commonly done in percentages.

How to convert nits to lumens?

1 Nit = 3.426 Lumens. To convert nits to lumens simply multiply the number of Nits by 3.426.

How to convert lumens to nits?

Divide the number of Lumens by 3.426.

Conclusion

Understanding the nits, lumens, and luminance specifications is an important factor when choosing light-emitting devices such as LCD screens. However, there are other specifications to consider, such as refresh rate, interface, viewing angle, and resolution. Reach out to one of our engineers today to help you choose the perfect display for your application.