[JonathonW]

What you're seeing here is Apple's EDR implementation [1], which, on non-local dimming displays (every Mac display except the M1/M2 14" and 16" MacBook Pros and the Pro Display XDR), works by bumping up the whole display brightness (and adjusting brightness of all non-HDR content downwards) to display colors brighter than standard SRGB white.

So, yeah, both QR codes probably are brighter on your old Pro, if its display brightness is set higher. And, if you adjust display brightness on the Air, you'll see them converge to the same brightness there, too (on my M2 Air, it seems that Apple leaves a little headroom for the HDR "white" to appear a bit brighter than UI white at full brightness; not sure if the M1 Air behaves the same or not as it has an older display).

Displays with local dimming (and OLEDs) can display, in small areas, colors that are brighter than the maximum full-screen brightness. That's where HDR content gets really compelling-- if all you can do is dim the whole screen, you're unlikely to see much of anything that you couldn't do just by bumping up the brightness with SDR content.

[1] https://prolost.com/blog/edr

[nwienert]

Does this mean some type of monkey patch could force the M2 screen to display a bit brighter? Because that’s my biggest gripe with it, I wish the screen would get to at least double the current max brightness.

[account42]

Selling screens with only a global backlight or edge-lit panels as "HDR" is basically fraud.

[bhaney]

Very interesting. Thanks for the explanation!