Kelvin to mired, and the mired shift
Mired is one million divided by the color temperature in kelvin: 3200 K is 312.5 mired and 5600 K is 178.6. The shift from one to the other is the difference, here 133.9 mired, and a gel closes it: a positive shift warms (CTO), a negative one cools (CTB).
The shift
+133.9 mired
Positive: the light needs warming, which is CTO.
Mired to one decimal place; kelvin rounded to the nearest 10 K. Open these two lights in the gel calculator.
What mired is, and why gels use it
Mired is short for micro reciprocal degree: one million divided by the color temperature in kelvin. It turns kelvin inside out so that equal steps look like equal changes in color. A 500 K step is huge at the warm end and small at the cool end: 2700 K to 3200 K is a shift of 57.9 mired, while 5600 K to 6100 K is only 14.6. That is why two lights 500 K apart can be a problem indoors and invisible outdoors.
Gels are rated in mired because a sheet moves any light by about the same number of mired wherever it starts. LEE's Full CTB takes away 137 mired, so it turns a 3200 K lamp into roughly 5700 K and a 2700 K bulb into roughly 4300 K. In kelvin the same sheet looks like two different gels; in mired it is one number. Work out the gap in mired and the sheet follows.
How it works
The tool divides one million by each light, takes the difference, and calls it the shift: positive when the light you have needs warming toward the one you want (CTO), negative when it needs cooling (CTB). Then it runs the same gel search as Cutvey Meter and the gel calculator: one sheet or two, never orange and blue together, fewest sheets and smallest leftover first, and no gel under 6 mired. Type the lights in kelvin or straight in mired; the answer is the same.
Kelvin to mired
| Kelvin | Mired | A light near it |
|---|---|---|
| 1,900 K | 526.3 | Candle flame |
| 2,000 K | 500.0 | Sodium streetlight, roughly |
| 2,700 K | 370.4 | Household bulb |
| 3,000 K | 333.3 | Warm white LED or tube |
| 3,200 K | 312.5 | Tungsten film lamp |
| 4,300 K | 232.6 | Where the app's kelvin scale changes halves |
| 5,000 K | 200.0 | Some daylight LEDs |
| 5,600 K | 178.6 | Daylight, HMI |
| 6,500 K | 153.8 | Overcast sky |
| 7,500 K | 133.3 | Blue sky, open shade |
| 10,000 K | 100.0 | Deep blue shade |
Mired is 1,000,000 divided by the kelvin, to one decimal place. Lamp values are typical ratings; real lamps drift with age, dimming and voltage.
One sheet, four lights
| Lamp | Mired | With Full CTB (LEE 201, −137) | With Full CTO (LEE 204, +159) |
|---|---|---|---|
| 2,700 K | 370.4 | 4,290 K | 1,890 K |
| 3,200 K | 312.5 | 5,700 K | 2,120 K |
| 4,300 K | 232.6 | 10,460 K | 2,550 K |
| 5,600 K | 178.6 | 24,050 K | 2,960 K |
The same mired shift added to each lamp, rounded to the nearest 10 K. The kelvin change looks different every time; the mired change does not.
In the app
Meter shows the gap in mired while you point.
Pin one light with REF, or type a target from 2,000 to 10,000 K, then point at the next. The card shows the difference in kelvin, mired and tint, and MATCH when the two are within 5 mired.
Get Cutvey Meter