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To convert a measurement from candelas per square meter (cd/m²), also known as nits, to foot-lamberts (fL), you use the conversion factor that 1 fL is equal to 3.426 cd/m². Therefore, to convert from cd/m², you divide by 3.426.
Example:
A monitor has a brightness of 300 nits (300 cd/m²). Convert this to foot-lamberts.
300 cd/m² / 3.426 (cd/m²)/fL ≈ 87.56 fL
Answer: A luminance of 300 nits is equal to approximately 87.56 foot-lamberts.
Luminance is a photometric measure of the luminous intensity per unit area of light traveling in a given direction. In simpler terms, it describes the perceived brightness of a surface. It quantifies how much light is emitted from, passes through, or is reflected from a particular surface and falls within a given solid angle. Unlike illuminance (measured in lux), which quantifies the amount of light falling *onto* a surface, luminance quantifies the light *coming from* the surface. It is what characterizes how bright we perceive that surface to be.
For example, a movie screen in a dark theater has a certain luminance, which is the light coming from the projector and reflecting off the screen towards the audience's eyes. Two surfaces can have the same illuminance (the same amount of light hitting them), but have different luminance values if one is dark and absorbs most of the light while the other is white and reflects most of it. Luminance is a critical metric in display technology (for TVs, monitors, and smartphones), lighting design, and road safety. The SI unit for luminance is the candela per square meter (cd/m²), which is often referred to as a 'nit'. This converter helps translate between the nit and other historical or regional units of luminance.
Lᵥ = d²Φᵥ / (dΩ * dA * cos(θ)), where Φᵥ is the luminous flux, Ω is the solid angle, A is the area, and θ is the angle of emission.Lᵥ = (Eᵥ * R) / π.A nit is simply another name for the SI unit of luminance, candela per square meter (cd/m²). The term is very common when specifying the brightness of displays, like computer monitors, TVs, and smartphones. A higher nit value means a brighter screen.
This is a key distinction. Illuminance (measured in lux or foot-candles) is the amount of light that *falls on* a surface. Luminance (measured in nits or cd/m²) is the amount of light that is *emitted or reflected from* that surface. A black wall and a white wall in the same room have the same illuminance, but the white wall has a much higher luminance because it reflects more light.
A typical modern smartphone can reach a maximum brightness of about 400 to 600 nits for normal viewing. Some high-end phones designed for HDR video playback can have peak brightness levels that exceed 1000 nits in small portions of the screen.
High luminance (brightness) is crucial for a good viewing experience, especially for High Dynamic Range (HDR) content. It allows the TV to display bright highlights (like explosions or reflections of the sun) with more impact and realism, and it helps to overcome glare from ambient light in a bright room.
The candela (cd) is the SI base unit of luminous intensity. It measures the amount of light emitted by a source in a particular direction. Luminance, in cd/m², measures that intensity per unit of surface area.