calibratr

Your photos, the way you edited them.

Out of the box, a monitor rarely shows what is in the file: too cool, too blue, with greys that drift in the shadows. calibratr measures it with your iPhone's camera and turns that into an ICC profile for exactly that display. No colorimeter, no subscription.

iPhone app on the App Store Download the Mac app (DMG)

Both apps are free. A one-time purchase in the iPhone app unlocks installing the profile.

Vermeer's Milkmaid, on the left on a monitor running too cool, on the right after calibration before after
Effect computed from a simulated measurement: a monitor in its cool factory preset, before and after. Johannes Vermeer, The Milkmaid, Rijksmuseum, public domain.

How it works

  1. Prepare Darken the room. Switch off automatic brightness, on the Mac and in the monitor's own menu. Let the monitor warm up, an hour for an OLED. Then open the Mac app and choose “Start calibration”.
  2. 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.
  3. 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.
  4. Result A before and after picture appears on the iPhone and the Mac, with white point, gamma, contrast, gamut and grey balance. One click on the Mac installs the profile.

What calibratr does

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 %.

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: on the Mac on the measured monitor itself, on the iPhone recreated from the measurement. Computed, 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 Store

Mac 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.