Luminance Converter

Modern HDR (High Dynamic Range) displays for TVs and smartphones can achieve peak luminance values well over 1000 nits, allowing for very bright highlights and better contrast. Standard SDR (Standard Dynamic Range) displays typically range from 250 to 500 nits. Outdoor-readable displays often need 700 nits or more.

Units like the Lambert and Foot-lambert are based on the concept of a perfectly diffusing (or Lambertian) surface, which appears equally bright from all viewing angles. Real-world surfaces are rarely perfectly Lambertian.

While luminance is a physical measure, perceived brightness by the human eye is complex and also influenced by factors like adaptation, contrast with surroundings, and color.

The surface of the full moon has an average luminance of about 2,500 cd/m². Even though it seems very bright in the night sky, this is far less than a clear blue sky on Earth.

The term 'nit' became popular in the display industry because it's a short, simple term for a complex unit (candela per square meter). It effectively communicates the screen's brightness to consumers.

OLED displays can achieve perfect black levels (0 cd/m²) because each pixel generates its own light and can be turned off completely. This creates an 'infinite' contrast ratio, even if their peak luminance isn't always as high as the brightest LCDs.

Light pollution from cities creates 'sky glow,' which is a diffuse luminance in the night sky. This can be measured in units like cd/m² and is a major problem for astronomical observations.

Standard digital cinema projection specifies a screen luminance of 48 cd/m² (or about 14 foot-lamberts) for 2D content when viewed from the center of the auditorium.

Veiling luminance is stray light that is reflected from the surface of a display, reducing contrast and making the image harder to see. Anti-glare and anti-reflection screen coatings are designed to minimize this.

The 'skot' was a proposed unit of luminance for very low light levels, such as in scotopic (night) vision. It never gained widespread acceptance but highlights the need for different scales in photometry.

The bioluminescent light from a firefly is surprisingly bright in terms of luminance, but because the emitting area is so small, the total light output (luminous flux) is very low.

The 'vivid' or 'dynamic' picture mode on many TVs boosts the luminance to maximum levels to look impressive in a bright retail store. For home viewing in a dimmer room, these settings are often overly bright and can cause eye strain.

An important quality metric for a display is its luminance uniformity, which measures how consistent the brightness is across the entire screen. Cheaper displays may be noticeably brighter in the center than at the edges.

The luminance of the sun's surface is immense, about 1.6 billion nits. This is why you should never look directly at the sun, as it can cause permanent eye damage instantly.

The 'brightness' of paper is often measured by its reflectance. A white piece of paper under typical office lighting (500 lux) will have a luminance of about 120-150 cd/m², a comfortable level for reading.

The apostilb is another non-SI unit of luminance, equal to 1/π cd/m². It's equivalent to the luminance of a perfectly diffusing surface emitting or reflecting one lumen per square meter. The unit is sometimes called a 'Blondel' after the French physicist André Blondel.

The contrast ratio of a display is the ratio of the luminance of the brightest white to the darkest black. A high contrast ratio is crucial for image quality, allowing for deep blacks and vibrant colors.

Modern screens use ambient light sensors to implement adaptive brightness. They measure the surrounding illuminance (lux) and adjust the screen's luminance (nits) accordingly for optimal viewing and to save battery power.