calibratr
Repeatable
The camera measures in RAW at a fixed exposure, with no white balance or image processing. Two runs on the same monitor agree to within 1 %.
Your iPhone is the instrument.
calibratr calibrates your monitor with your iPhone's camera. The Mac shows colour patches, the iPhone measures them. The result is an ICC profile for exactly that display. No colorimeter, no subscription.
Both apps are free. A one-time purchase in the iPhone app unlocks installing the profile.
How it works
- Prepare Darken the room, switch off automatic brightness, let the monitor warm up for 30 minutes. Open the Mac app and choose “Start calibration”.
- Pair Scan the QR code on the screen with the iPhone app. Both devices on the same Wi‑Fi; the connection stays on the local network.
- Measure Hold the iPhone a hand's width from the centre of the screen and start there. The measurement takes one to ten minutes depending on scope.
- Result White point, gamma, contrast, gamut, grey balance and a before/after comparison appear on the Mac. One click installs the profile.
What calibratr does
Checked sensor
Before every run the iPhone checks its sensor and subtracts its noise floor.
A real ICC profile
macOS uses it like any other colour profile. Target: native, sRGB, or D65 with gamma 2.2.
Verifiable
Extra patches check the finished profile. The report shows the deviation in ΔE.
Before and after
Three pictures with skin tones, black and white and saturated colours, with a slider between uncalibrated and calibrated. Computed from the measurement, not photographed.
Light meter, no Mac needed
The iPhone app also measures on its own: colour temperature, white point, tint and exposure of any glowing surface, whether monitor, lamp or window.
iPhone app
Free on the App Store. Needs an iPhone with a RAW-capable camera and iOS 16 or later. Scan the code or open the link.
iPhone app on the App StoreMac app
Free, signed and checked by Apple. For macOS 13 or later, Apple Silicon and Intel.
Download the Mac app (DMG)The link always points at the newest version.
What it costs
Measuring, the report and the picture comparison cost nothing and stay free. The one-time purchase “Keep the result” in the iPhone app unlocks installing the profile on the Mac: for all your displays, for good. No subscription, no account.
What it cannot do
A phone camera is not a spectroradiometer. calibratr measures white point, grey balance and tone curves reliably, and takes the primaries from the monitor's factory profile. It cannot measure brightness in cd/m². If you need a reference instrument for prepress, you need a colorimeter. If you want your monitor neutral and repeatable, you do not.