Luminance Converter

You're spec'ing a display for a project and the manufacturer reports brightness in candelas per square meter. Your reference document is in nits. Lambert pops up in some optics texts. They're closely related, but you don't want to do the math by hand.

Good news: 1 nit equals 1 cd/m². Lamberts are the odd one out, with a factor of π in the conversion. Type a value into any of the three fields and the others update.

Most commercial displays land between 250 and 600 nits. HDR-capable screens push past 1,000. If you're seeing four-digit numbers in a spec sheet, that's why.

The math is simple once you know the relationship. Luminance measures light per area in a specific direction, usually quoted in candelas per square meter — that's exactly one nit. The lambert is older and uses a different convention: it measures luminance assuming the surface is a perfect diffuser scattering light evenly across a hemisphere, so it includes a factor of π. To convert, 1 lambert = 10,000/π nits ≈ 3,183 nits. The footlambert (used in older U.S. cinema specs) is 1/π × cd/ft^2, which converts to roughly 3.43 nits.

For modern display work you almost never need anything but nits. The full HDR specification chain — HDR10, Dolby Vision, HLG — is calibrated against reference monitors at specific nit levels. HDR10 mastering targets 1,000 or 4,000 nits depending on the studio. Cinema projection runs much lower, usually around 48 nits for a calibrated room because the eye adjusts to the dim viewing environment and higher would feel uncomfortable.

A worked example: you're sourcing a digital signage panel for an outdoor café. The spec sheet says '700 cd/m^2'; another option says '500 nits.' Same units, just labeled differently. The 700 nit panel will be readable in direct daylight, the 500 nit one will struggle in bright afternoon sun. Indoor signage where the ambient light is controlled can get away with 300–400 nits and still look punchy.

Where it goes sideways: comparing 'peak' versus 'sustained' brightness. A panel rated for 1,000 nits peak might only sustain 600 nits in full-screen white because of thermal limits. HDR mastering typically uses peak figures because real content rarely fills the whole screen with peak white. For video, the difference rarely matters; for static signage left on for hours, the sustained number is what you actually care about.