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.

Why Understanding Light Measurements Matters in Display Design

Brightness isn’t a one-size-fits-all metric. What looks clear in a dim environment may fade or wash out under direct sunlight. That’s why display performance depends on understanding how light is measured, and how those measurements apply to real-world conditions.

Terms like nits, lumens, and luminance are often used interchangeably, but each serves a different purpose. Knowing the difference between nits vs lumens provides a more accurate path to selecting the right display from the start.

ライトコンセプツ

光の測定単位を比較する前に、いくつかの概念を理解することが必要です。

• 照度。ある面に当たる光の量。(その表面がどのように照らされているか）。
• 輝度。物体から放射される光の知覚量。輝度は、明るさとも呼ばれる。
• ルーメン：光源から放射される可視光線の総量。光束を測定する単位である。
• 光束（Lux）。あらゆる方向に放射される光の量で、ルーメン単位で測定される。
• 光度。光源から単位立体角あたり特定方向に放射される可視光線の量。カンデラは光度のSI単位である。
• カンデラ：光の強さを表す単位。カンデラとは、任意の地点からの単一方向の輝度量を測定するものである。

ろうそく1本の光は、およそ1カンデラです。スポットライトやレーザーは、光のほとんどが一方向に集中するため、カンデラ値が最も高いものがあります。

詳しくはこちら液晶ディスプレイの種類

光量測定単位

人間の目で見た明るさを基準にして光を測ることができる。光を測るのに最もよく使われる単位は、ルーメン、ルクス、カンデラです。

光国際単位系（SI）

ニッツ

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. 

1NITは、1平方メートルあたり1カンデラに相当します。同じ種類の量を表すだけでなく、等価な単位でもあるのです。

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.

How Nits Affect Real-World Display Performance

Nits measure luminance, or the brightness emitted from a display’s surface in a specific direction. This directly impacts how well the screen can be seen in different lighting conditions. A display may appear bright indoors but lose visibility in environments with strong ambient light if the nit level is too low.

For most indoor applications, 250 to 400 nits is usually sufficient. In outdoor or high-glare settings, displays typically require 700 nits or more to maintain legibility. Industrial controls, medical equipment, and automotive interfaces often fall into this higher range.

ルーメン

ルーメン（lm）は、国際単位系（SI）における光束の測定単位である。光束とは、光源から放射される光の量をルーメンという単位で表したものである。ルーメンは、電球の製品仕様で光の明るさを表すのによく使われる。プロジェクターの光出力もルーメン単位で測定されるのが一般的です。

ルーメン vs カンデラ

ルーメンは全方向の光量を表し、カンデラは単一方向の特定点からの光量または強度を表します。

ニット数 vs ルーメン数

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.

カンデラ vs ニット

1カンデラ＝1ニット。名前以外にカンデラとニットの違いはありません。

ルミナンス

輝度（Lv）は、物体から放射される光、反射される光、または物体を通過する光の量を測定するものです。輝度はカンデラ毎平方メートル（cd/m²）で測定される。

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

Misconceptions About Brightness and Display Quality

Brightness is often used as a shorthand for display quality, but that can lead to incorrect assumptions. Here are some common misconceptions:

• Higher brightness always means better visibility: Not always. A display rated at 1000 nits might look washed out if contrast is poor or if glare isn't managed. In some cases, a lower-brightness display with optical enhancements will perform better.

• Boosting nits solves all outdoor readability issues: Brightness is just one piece. Optical bonding, anti-reflective coatings, and panel type (like IPS vs standard TFT) all affect how readable a display is in bright conditions.

• Lumens and nits can be compared directly: Lumens measure total light output from a source. Nits measure how bright a display surface appears to the viewer. These are separate measurements used in different contexts. In displays, nits vs lumens is not an apples-to-apples comparison.
• All high-brightness displays behave the same in the field: Two displays with the same nit rating can still look very different. Factors like color accuracy, viewing angle, and ambient light handling influence real-world performance.

Choosing the Right Brightness for Your Application

Lighting conditions play a major role in display performance. Brightness levels that perform well indoors may not be visible in high-glare outdoor conditions.

• Indoor use: In environments like test stations, lab instruments, or control rooms, 250 to 400 nits is usually sufficient. The goal here is comfort and clarity without unnecessary intensity.
• Mixed lighting or partial sun: For equipment exposed to overhead lights, windows, or indirect sunlight, displays in the 400 to 700 nit range offer improved readability without excessive power draw.
• Direct sunlight or harsh glare: Displays used outside or in high-glare areas need to be at least 700 nits to remain legible. This is common in automotive, marine, and industrial field equipment.

よくあるご質問

輝度は何で測られるのですか？

1平方メートルあたりのカンデラ（cd/m²）。

光束と光度の違いは何ですか？

光束は、光源が全角度にわたって放射する光の総量を測定する。これに対して光度は、光源がある方向に放射する光の量を表す。

ルミナンスとイルミナンスの違いは？

輝度は光源から放射される光の量であり、照度は表面に当たる光の量である。

明るさと輝度は同じですか？

明るさは輝度とは異なり、定量的な指標はない。輝度は知覚であり、一般的にはパーセントで行われる。

nitsをルーメンに変換する方法は？

1Nit＝3.426ルーメンです。Nitをルーメンに変換するには、Nit数に3.426を乗じるだけです。

ルーメンをニットに変換する方法は？

ルーメン数を3.426で割る。

結論

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.