When people say “white balance,” they usually mean Kelvin - the warm/cool slider. But Kelvin is only half of the story. The other half is tint - the magenta/green axis. Get one right and the other wrong, and your skin tones still look bad.
Two axes, not one
Imagine a 2D plane:
- Horizontal axis = Kelvin: orange (low) → blue (high)
- Vertical axis = Tint: green (low) → magenta (high)
Every light source sits somewhere on this plane. A tungsten bulb is warm and neutral tint. A fluorescent tube is neutral Kelvin but green tint. A cheap LED can be daylight Kelvin but heavy green tint.
White balance fully corrects only when both axes are right.
Why “looks green” is a tint problem
A fluorescent tube at 4500K emits a spiky, discontinuous spectrum. Even when you tell your camera “this light is 4500K,” whites might still come out faintly green. That’s because the light’s spectrum is missing red wavelengths and full of green - a problem Kelvin cannot describe.
To fix it, you add magenta tint in the camera (or pull green out in post). The light is now neutralised on both axes.
The same is true of:
- Cheap or older LEDs - usually skew green
- Sodium-vapour street lights - skew yellow/green
- Mixed practicals - one bulb is warm and neutral, the next is cool and green
Where tint matters most
- Skin tones. Green tint = sickly. Magenta tint = sunburnt. The human eye is unbelievably sensitive here.
- Greenscreen / VFX shoots. A slight green cast on talent bleeds into the matte.
- Product photography. Whites and neutrals shift colour visibly.
- Interview lighting. Practical lamps and key lights almost never match on the tint axis.
How to actually correct tint
On set, before recording:
- Meter the dominant light with KEV - it shows both Kelvin and magenta/green tint.
- Set the camera’s Kelvin to the value KEV reports.
- Set the camera’s tint (or “CC”, “Magenta/Green”, “+/-“) to the value KEV reports.
Most cinema and Blackmagic cameras expose tint as a separate field. Most stills cameras only let you set Kelvin - if that’s your case, plan to fix tint in the colour pass in post.
On the lights themselves:
- Add a Minus Green gel on green-skewing fluorescents or LEDs.
- Add a Plus Green gel on magenta-skewing sources.
- Modern bi-colour LED panels expose a green/magenta dial - tune it to match the practicals.
A practical example
You’re shooting an interview. Key light: a 5500K daylight LED panel. Background: room with fluorescent tubes overhead.
You set the camera to 5500K to match the key. The interview subject looks good. The background looks sickly green because the fluorescents are pushing green.
Two ways out:
- Lower the camera’s tint toward magenta - but then the subject looks slightly magenta too.
- Gel the fluorescents with minus-green - now the background neutralises without affecting the key.
A meter that reads tint - like KEV - tells you how much to gel before you waste time guessing.
Every camera measures tint in different units
There is no shared scale for tint the way there is for Kelvin, which is why a tint value does not transfer between bodies.
| System | Units | Notes |
|---|---|---|
| Canon | CC, in steps of 1 | 1 CC = 5 mireds. Positive is green, negative is magenta |
| Sony | G/M, in steps of 0.25 | Reversed from Canon: positive is green |
| Nikon | A-B / G-M grid | Two-axis pad, roughly 5 mireds per step |
| Blackmagic | Tint, -50 to +50 | Positive is green. Sits next to the Kelvin field |
| ARRI | CC, -12 to +12 | 1 CC = 1/8 green or magenta gel |
| Lightroom / Camera Raw | Tint, -150 to +150 | Positive is magenta - opposite sign to most cameras |
| DaVinci Resolve | Tint, -100 to +100 | Positive is magenta |
Two traps in that table. First, the sign flips between camera bodies and grading software, so a value copied straight across doubles the error instead of fixing it. Second, ARRI’s CC unit is calibrated to gel strengths, which makes it the only scale that translates directly to something you can put in front of a lamp.
The practical answer: note the tint your meter reports, then find the value on this body that neutralises a grey card. Write it on the camera tape. Do not assume it carries to the second camera.
The gel reference
Correcting at the light beats correcting at the camera, because it fixes the source for every camera pointed at it.
| Gel | Corrects | Typical use |
|---|---|---|
| Full Minus Green | Strong green cast | Older fluorescent tubes |
| 1/2 Minus Green | Moderate green | Cheap LED panels, newer tubes |
| 1/4 Minus Green | Light green | Good LEDs that still skew slightly |
| 1/8 Minus Green | Barely-there green | Final match between two nearly-identical sources |
| Full Plus Green | Strong magenta cast | Matching a tungsten key to fluorescents |
| 1/2 Plus Green | Moderate magenta | Some HMIs, certain daylight LEDs |
Minus Green is sometimes sold as “minusgreen” or under the number 3308; Plus Green as 3304. The naming says what the gel removes from the light, not what colour the gel looks - a Minus Green gel is visibly magenta.
Start at the strength your meter suggests, then re-meter. Gels are subtractive: doubling a 1/4 does not equal a 1/2, and stacking them costs you real stops of output.
CRI, TLCI and what tint cannot tell you
Kelvin and tint together describe a light’s colour with two numbers. Some lights need more than two.
A cheap LED can meter at a perfectly respectable 5500K with near-zero tint and still render a red jumper as brown. That happens when the light’s spectrum has gaps - there is simply no red energy in it for the jumper to reflect. No white balance setting recovers a wavelength that was never emitted.
The metrics for this are separate:
- CRI (Ra) - averaged accuracy across eight pastel test colours. Above 95 is good; 80 is poor. Widely quoted and easily gamed.
- R9 - specifically deep red, the one CRI’s average hides. A light can score CRI 90 and R9 near zero, which is why skin looks lifeless under it.
- TLCI - the broadcast equivalent, weighted for how a camera sensor responds rather than how an eye does. More relevant than CRI for video.
- SSI - compares a light’s full spectrum against a reference. The most rigorous and the least commonly published.
A colour meter (including KEV) reports Kelvin and tint. Full spectral metrics need a spectrometer. The practical takeaway: if a light meters clean but the image still looks wrong, the problem is spectral, and the fix is a different light - not a different setting.
Fixing tint in post
When the camera has no tint field, the correction moves to the grade.
In Lightroom or Camera Raw: use the White Balance eyedropper on something genuinely neutral - a grey card, a white shirt in the same light, paper. It sets Kelvin and Tint together. Remember the sign is reversed from most cameras: dragging Tint positive adds magenta.
In DaVinci Resolve: the Temp and Tint controls in the primaries wheels work on log or RAW. For a green cast confined to one part of the frame - the classic case being fluorescents behind a properly lit subject - use a qualifier or a window rather than a global correction, or you will drag the subject magenta while fixing the background.
What post cannot fix: a green cast in a single channel that clipped in camera, and a green cast on a greenscreen shoot, where it has already contaminated the matte. Both have to be handled on set.
TL;DR
| Problem | Kelvin or tint? | Fix |
|---|---|---|
| Image too warm/orange | Kelvin | Raise camera Kelvin |
| Image too cool/blue | Kelvin | Lower camera Kelvin |
| Skin looks green | Tint | Add magenta tint, or gel light with minus-green |
| Skin looks pink/magenta | Tint | Subtract magenta tint, or add plus-green |
| Whites look green AND warm | Both | Set Kelvin first, then tint |
Kelvin alone won’t save you under fluorescents or cheap LEDs. Meter both axes, set both, then shoot.