What is mired and why is it used?

Mired (micro reciprocal degree) is calculated as 1,000,000 / Kelvin. The advantage of mired over Kelvin is that equal mired shifts produce equal perceived colour changes regardless of the starting temperature. A shift of 50 mired always looks the same, whereas a shift of 500K looks very different at 2000K vs 8000K.

What colour temperature is daylight?

Direct midday sunlight is approximately 5200K. Overcast sky is around 6000-6500K (bluer). Open shade under blue sky can be 7500-10000K. Flash units are typically calibrated to 5500K. Golden hour light drops to around 3500-4000K.

What are CTO and CTB filters?

CTO (Colour Temperature Orange) filters warm light by adding positive mired shift. CTB (Colour Temperature Blue) filters cool light by adding negative mired shift. A full CTO converts daylight (5500K) to tungsten (3200K), a shift of about +131 mired. These are used on flash units and studio lights to match ambient colour temperature.

Should I set white balance in camera or in post?

If shooting RAW, white balance can be changed in post-processing with no quality loss — it is simply metadata. However, setting it correctly in-camera gives you accurate preview images and histograms. If shooting JPEG, white balance is baked in and should be set accurately before shooting.

PhotoCalcs

White Balance Calculator — Kelvin & Mired Conversion

Convert between colour temperatures in Kelvin and mired, and find the right colour correction filter.

Light SourceColour temperature of the light you are shooting under (pick a preset or Custom Kelvin)

Target Kelvin

Desired white balance setting

How We Calculate This

This calculator converts between Kelvin and mired values and suggests correction filters:

Mired Conversion

Mired = 1,000,000 / Kelvin

Mired Shift

Shift = target mired - source mired

Positive shift = warming (towards orange/tungsten). Negative shift = cooling (towards blue/daylight). The calculator suggests the nearest standard CTO or CTB gel that is at least strong enough for the required shift — pick the next size up rather than under-correct. Published gel values vary slightly by maker (Rosco vs Lee): Full CTO ≈ +159 to +167 mired, ¾ ≈ +124, ½ ≈ +81, ¼ ≈ +42 to +64, ⅛ ≈ +20 to +26; CTB values are the negative mirror.

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Last updated: February 2026

All calculations are estimates based on standard optical and photographic formulas. Results may vary with specific equipment.