Monitor calibration by eye — matching two monitors
The order to follow when you have no colorimeter — and when two monitors disagree.
Calibrate a monitor by eye with no hardware. Set brightness, contrast, gamma and colour temperature in the right order, and put two monitors side by side to match them.
Start with the room lit the way it normally is while you work. Values set in a bright room look wrong at night.
1. Brightness — the black ramp
Raise the monitor brightness until the two leftmost patches (0 and 2) are distinguishable from each other. If the white at the far right is dazzling, it is too high.
2. Contrast — the white ramp
The three rightmost patches (247, 251, 255) should each be distinct. If they merge, lower the contrast.
3. Gamma
Step at least a metre back from the screen. The panel where the stripes and the centre square look equally bright is your current gamma. Aim for 2.2.
4. Uniformity and grey scale
A red or blue cast across the grey strip means the colour temperature is skewed. Lower the dominant channel in your monitor’s RGB gain.
5. Matching two monitors
Open the panel below full screen, then straddle the browser window across both monitors. With the same colour on both screens at once the difference is obvious. Bringing the brighter one down to the darker one is easier on your eyes.
Half the job is doing it in the right order
Brightness, then contrast, then gamma, then colour temperature. Change the order and each step undoes the one before it. Adjust only the monitor's own OSD at each stage and leave the graphics driver's colour settings at default until the very end — touching both at once makes it impossible to tell which one caused what.
Why two monitors never quite agree
Different panel types (IPS against VA, or simply different manufacturers) have different colour gamuts and gamma curves, so identical is not achievable. The realistic target is matching the colour temperature and brightness of white. Those two alone remove most of the jolt you feel dragging a window across.
A laptop plus an external monitor
Laptop panels are usually brighter and cooler than desktop monitors. Rather than pushing the external display up to match the laptop, bring the laptop down to the external — easier on your eyes and better for battery. On macOS you can adjust colour temperature in the display profile in System Settings.
What this method cannot do
Calibrating by eye uses your own adaptation as the reference, so it is not repeatable. If you need to match printed output, or photo and video work is your job, you need a colorimeter. For office and development work the four steps above are enough.
Brightness — get this wrong and everything after it is wrong
Monitor brightness has to match the light in the room. A level that felt right under office lighting is painful at night. The test is simple: open a document with a white background, and if it looks like paper the level is right; if it looks like it is glowing, it is too high. Fixing brightness first means every colour you judge afterwards is the colour you will actually work in.
How contrast differs from gamma
Contrast sets the distance between the brightest white and the darkest black. Push it too far and the bright steps merge, so the folds in a white shirt disappear. Gamma sets how the mid-tones are distributed between those ends. Low gamma washes the whole image out; high gamma buries the shadows. The general standard is 2.2, which is what most monitors ship with.
Why 6500K is the reference
6500K approximates midday daylight, which is why it is the baseline when comparing against prints or photographs. Higher reads cool and blue, lower reads warm and yellow. Lowering it is genuinely easier on your eyes at night, but set it back to 6500K while you are matching colour. Night mode and blue-light filters must be off during calibration — leave one on and everything you set will be wrong in daylight.
Grey shows differences better than white does
Your eyes adapt to white quickly, so two slightly different whites start looking identical within seconds. Mid-grey makes the direction of a cast far more obvious. Put the same grey on both screens and butt the edges together. If one side reads red or blue, lower that channel rather than raising the others — reducing costs less brightness than adding.
Frequently asked
Is calibrating by eye worth doing without a colorimeter?
For office and development work, yes. Getting brightness and colour temperature close removes most of the jolt when you drag a window between screens. But if you need to match printed output, or photo and video work is your job, calibrating by eye is not repeatable enough and you need a colorimeter.
Can I make two monitors truly identical?
No. Different panel types have different gamuts and gamma curves, so identical is not achievable. The realistic goal is matching the colour temperature and brightness of white — those two alone remove most of the visible mismatch.
Can I calibrate with a blue-light filter on?
No. The filter lowers colour temperature artificially, so anything you set with it on will be wrong once you turn it off. Disable night mode and blue-light filters for the whole calibration.