The reference stack projects approximately 3189 K, leaving a −1.07 mired residual to the target. Verify the real source and gel before a critical match.
Matches are ranked by residual mired shift. Published shifts are product references, not universal values for every gel brand or light spectrum.
| Option | Reference shift | Projected result | Residual to target |
|---|---|---|---|
| ½ CTO + ⅛ CTO | +135 mired | 3189 K | −1.07 mired |
| ½ CTO | +109 mired | 3477 K | +24.93 mired |
Kelvin is not a linear correction scale. A 500 K change near tungsten is much larger in reciprocal-temperature terms than a 500 K change in high daylight. Mired—short for micro reciprocal degree—makes these lighting corrections easier to compare.
mired = 1,000,000 ÷ kelvin
kelvin = 1,000,000 ÷ mired
required mired shift = target mired − source mired
Adding a positive mired shift increases the reciprocal value and therefore lowers Kelvin, producing a warmer result. Adding a negative shift lowers the reciprocal value and raises Kelvin, producing a cooler result.
Use an orange or warming correction when the target Kelvin is lower than the source. Example: 6500 K to 3200 K is approximately +158.65 mired.
Use a blue or cooling correction when the target Kelvin is higher than the source. Example: 3200 K to 5700 K is approximately −137.06 mired.
The calculator uses the following published LEE Filters values to make its reference comparisons. Fractional names do not represent an exact linear fraction of the full filter's mired shift, so the listed values—not the fraction labels—drive the matching calculation.
| Correction | Reference product | Published mired shift | Published example |
|---|---|---|---|
| Full CTO | LEE 204 | +159 | 6500 K to 3200 K |
| ½ CTO | LEE 205 | +109 | 6500 K to 3800 K |
| ¼ CTO | LEE 206 | +64 | 6500 K to 4600 K |
| ⅛ CTO | LEE 223 | +26 | 6500 K to 5550 K |
| Full CTB | LEE 201 | −137 | 3200 K to 5700 K |
| ½ CTB | LEE 202 | −78 | 3200 K to 4300 K |
| ¼ CTB | LEE 203 | −35 | 3200 K to 3600 K |
| ⅛ CTB | LEE 218 | −18 | 3200 K to 3400 K |
Technical references: LEE Filters product data for Full CTO, Half CTO, Quarter CTO, Eighth CTO, Full CTB, Half CTB, Quarter CTB, and Eighth CTB. Kodak's Wratten filter tables independently publish conversion temperatures and signed mired shifts and caution that filtration values are approximate.
| Source → target | Source mired | Target mired | Required shift | Direction |
|---|---|---|---|---|
| 6500 K → 3200 K | 153.85 | 312.5 | +158.65 | Warm / CTO |
| 5600 K → 3200 K | 178.57 | 312.5 | +133.93 | Warm / CTO |
| 3200 K → 4300 K | 312.5 | 232.56 | −79.94 | Cool / CTB |
| 3200 K → 5700 K | 312.5 | 175.44 | −137.06 | Cool / CTB |
This calculator treats the entered values as ideal correlated color temperatures and models gel shifts by addition on the mired scale. A real source is a spectrum, not just a Kelvin number. Two fixtures can share a CCT while differing in spectral power distribution, green-magenta tint, color rendering, output, and camera response. Gel also absorbs light; this tool does not calculate exposure loss.
Stacked-gel shifts are added as a planning approximation. Transmission curves interact, and heat, fading, angle, fixture optics, dimming, and product variation can change the result. For matching cameras, LEDs, discharge sources, or critical color work, check the manufacturer's current data and measure the corrected light with a suitable color meter or spectrometer.
A mired is one million divided by color temperature in kelvins. Because it is reciprocal, the scale better reflects the size of color-temperature corrections across warm and cool sources.
Divide 1,000,000 by the Kelvin value. The same formula in reverse converts mired to Kelvin: 1,000,000 divided by mired.
A positive shift moves toward a lower, warmer color temperature and normally calls for CTO-type correction. A negative shift moves toward a higher, cooler color temperature and normally calls for CTB-type correction.
The exact arithmetic is approximately +133.93 mired. That does not map universally to one gel name because manufacturers publish different shifts. This page compares specific reference values and shows the projected residual so you can choose a starting point, then test the actual source and material.
No. CCT compresses a complex spectrum into one value. Green-magenta tint, spectral gaps or peaks, color rendering, fixture age, dimming, and camera spectral response can still make nominally equal-CCT lights look different.
No. White balance changes the camera's interpretation of the complete scene. Gel changes the spectrum of one physical source before it reaches the subject. White balance cannot independently align two differently colored sources in the same shot.
No. Conversion, matching, clipboard text, and CSV creation run locally in the browser. The page does not send your source or target inputs to a backend.