Kelvin

What this is about

The scale trips up newcomers because physics and everyday language point in opposite directions: a candle at roughly 1800 K reads as warm, a blue midday sky at 10000 K reads as cold, yet the cold-looking light carries the higher number. On set the numbers work as shorthand. A DP asking for 4300 K is asking for a compromise between window and lamp; a gaffer setting an LED to 2700 K is matching household bulbs in shot.

A term only helps when everyone on set means the same thing by it — so what follows is how it is used, not a dictionary definition.

What runs differently here

In planning terms, that means:

• Higher Kelvin means bluer light, lower Kelvin means more orange — the opposite of how warm and cold are used in speech.
• Equal Kelvin steps are not equal visual steps; the mired scale exists because gel makers needed even increments.
• Household bulbs around 2700 K, film tungsten at 3200 K and daylight at 5600 K are the three anchors worth memorising.

With TillyGen

Lighting notes in TillyGen name a Kelvin value per setup, so the LED presets on the day match what was agreed in the lighting plan.

Change one constraint and the consequences travel through the whole plan: affected shots are flagged, the call sheet is regenerated, and nobody keeps working from yesterday's version.