Mired Shift Filter Calculator
Calculate the mired shift between two color temperatures to choose the right warming or cooling filter for your camera, video, or film stock.
Mired Shift
Mired (micro-reciprocal-degree) is the unit photographers use to describe color-correction filter strength. Unlike kelvin, mired values are linear — adding the mired value of a filter to the source’s mired gives the resulting mired exactly.
Formula
mired = 1,000,000 / temperature(K)
mired_shift = mired_target − mired_source
If mired_shift is positive, you need a warming (yellow / orange / amber) filter. If negative, you need a cooling (blue) filter.
Worked Example — Tungsten Film in Daylight
- Tungsten-balanced film: 3200 K → 312.5 mired
- Daylight: 5500 K → 181.8 mired
- shift = 181.8 − 312.5 = −130.7 mired
A negative shift of about 130 mired matches a Wratten 80A blue conversion filter — exactly what is sold for shooting tungsten film outdoors.
Common Filters and Their Mired Shifts
| Filter | Shift (mired) | Use |
|---|---|---|
| 81A (light warming) | +18 | Slight warming |
| 81B | +27 | Open shade in spring/fall |
| 81C | +35 | Strong warming for shade |
| 85B (full CTO) | +131 | Daylight film under tungsten |
| 80A (full CTB) | −131 | Tungsten film in daylight |
| 82A (light cooling) | −18 | Slight cooling |
| 82B | −32 | Mid cooling |
CTO and CTB in Video / Cinema Lighting
Cinematographers describe gels by Color Temperature Orange (CTO) and Color Temperature Blue (CTB):
- 1/8 CTO ≈ +20 mired
- 1/4 CTO ≈ +42 mired
- 1/2 CTO ≈ +81 mired
- Full CTO ≈ +167 mired
- 1/4 CTB ≈ −30 mired
- 1/2 CTB ≈ −68 mired
- Full CTB ≈ −137 mired
These cinema gels are designed in mired increments precisely because mired add linearly while kelvin do not.
Why Not Just Kelvin?
Adding 1000 K shifts a 3000 K source to 4000 K. Adding the same filter (call it +83 mired) to a 5000 K source produces 4286 K. Filter strength is fixed in mired but changes in kelvin depending on the source. That is why filter manufacturers spec mired and not kelvin.
Caveats
Mired only handles the color temperature axis — it does not address green/magenta tints from fluorescent and LED sources. For those, you also need plus-green or minus-green correction (CC filters or Rosco / Lee gel equivalents). A spot-on mired calculation still leaves a residual green tint that must be filtered separately.