Before anything else: this page is published by the makers of KEV, one of the apps listed below. I have tried to be straight about what KEV does not do and where other apps are better, because a comparison that concludes “buy ours” for every use case is worth nothing to you. Judge the reasoning, not the byline.
First, decide which measurement you need
“Light meter” is used for two unrelated instruments, and buying the wrong one is the most common mistake here.
- Exposure metering answers how much light is there and gives you f-stop, shutter and ISO. You need it when the camera’s own meter cannot be trusted: film cameras with no meter, strobes that fire too fast for the camera to read, high-contrast scenes where you want to place a specific tone.
- Colour metering answers what colour is this light and gives you Kelvin and tint. You need it when colour has to match: two cameras, an interview under mixed sources, product work, anything cut together from takes shot hours apart.
Most apps do one. Almost none do both well.
The apps worth considering
| App | Measures | Price | Best for |
|---|---|---|---|
| Cine Meter II | Incident + spot exposure, false colour, waveform | ~$25 | Cinematographers who want a real exposure meter |
| myLightMeter Pro | Reflected + incident exposure | ~$5 | Film shooters and classic stills workflows |
| KEV | Colour temperature + magenta/green tint | $2.99 | Setting white balance, matching cameras |
| Lumu (with dongle) | Exposure, colour, illuminance | ~$300 hardware | People who want hardware accuracy in a phone workflow |
| Photometer Pro | Reflected exposure | ~$10 | Simple, no-frills spot metering |
Cine Meter II
Written by Adam Wilt, who has a long background in video engineering, and it shows. Incident metering with an accessory diffuser, spot metering, a waveform monitor and false-colour exposure display. It is the closest thing on iOS to a serious exposure meter, and the interface assumes you already know what an incident reading is. It does not do colour temperature.
myLightMeter Pro
A focused, long-maintained reflected and incident exposure meter with a deliberately analogue interface. Popular with film photographers because it does exactly one job and does not get in the way. Cheap. No colour metering.
KEV
Reads colour temperature in Kelvin and magenta/green tint in real time through the rear camera, calibrated against a Sekonic C-700R-U SpectroMaster. One-time purchase, runs on iPhone, iPad and Apple Watch.
What it does not do: exposure. It will not give you an f-stop. If you came looking for an incident exposure meter, Cine Meter II is the answer, not this. The two are complementary rather than competing - many people carry one of each.
Lumu
A hardware dongle that plugs into the phone and does exposure, colour and illuminance with a real sensor. Around $300, so it sits between the app tier and the Sekonic tier. Genuinely more accurate than any camera-based app, and genuinely another object to carry and charge.
What separates a usable meter from a useless one
Not hardware versus software. Calibrated versus not.
An app that infers a reading from the camera sensor has to map that sensor’s response onto real-world values, and that mapping only exists if somebody measured known sources with a reference instrument and fitted the results. That work costs money, which is why it does not happen in free ad-supported apps.
An uncalibrated free meter will still display three confident digits. The number is decoration.
Test any meter in ten minutes
Do this before a paid job, not during one.
- Meter a known source. A 5500K daylight LED panel, or a camera flash. A calibrated colour meter should land within a couple hundred Kelvin of the marked value. For exposure, compare against a camera you trust in the same light.
- Read the same source three times, moving between reads. The spread should be small. A meter that wanders 500K on unchanging light is guessing.
- Check both ends. A tungsten bulb around 2900K and open north sky around 7500K. Errors grow at the extremes even when the middle looks right.
- Confirm against a grey card. Meter, dial the value into the camera, shoot the card, check the histogram. Equal RGB channels means the meter and your camera agree - which is what actually matters.
- Re-test after an iOS update. Rare, but camera pipeline changes have moved app readings before.
Step four is the real test. A meter that reads “wrong” by 200K but produces neutral files on your camera is more useful than one that is laboratory-correct and does not.
Recommendations by use case
| You are | Get |
|---|---|
| Shooting film with an unmetered body | myLightMeter Pro, or Cine Meter II |
| A DP wanting incident readings on set | Cine Meter II |
| Setting white balance across cameras | KEV |
| Fighting a green cast under office lighting | A meter that reads tint, not just Kelvin |
| Shooting product or e-commerce | A colour meter plus a grey-card workflow |
| Wanting one device to do everything | Lumu, or a hardware Sekonic |
| Just curious what the light is doing | Any calibrated app; start cheap |
The honest summary
There is no single best light meter app, because “light meter” covers two different instruments. Work out whether your problem is exposure or colour first - that decision eliminates most of the list immediately.
If the problem is colour, and it usually is for anyone shooting video under mixed interior lighting, then what you need is a Kelvin and tint reading you can dial straight into the camera. That is what KEV does, and the comparison against hardware colour meters covers where a phone stops being enough.