Why does a gamma test look different when I enable HiDPI?

A gamma test made from fine alternating lines depends on how those lines reach the panel’s pixels. HiDPI rendering, image resizing and fractional scaling can change the pattern itself. A different result after switching modes does not by itself show that the monitor’s gamma changed.

The macOS scaling explanation compares fractional scaling and pixel mapping.

For a pixel-pattern comparison, use the panel’s native-resolution LoDPI mode and display the test image without resizing it. Check browser or image-viewer zoom as well: the important condition is one image pixel per physical display pixel, not just a resolution label. Keep the monitor’s picture settings, HDR state and color profile unchanged while comparing.

Browser color management also affects web tests, as the EIZO monitor test explains. A screenshot viewed at another size or on another device adds another rendering path and cannot establish the original panel’s gamma.

Do not adjust gamma solely to make a resampled line pattern agree with its reference. If ordinary images still show crushed highlights or washed-out colors, investigate that separately. See output-range mismatches and text clarity after enabling HiDPI. A precise calibration requires measurements. This visual comparison only helps separate a scaling artifact from another color problem.