#ultrarunning
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Apple Watch Ultra 4 Hands-On: 24 New Things Tech Deep-Dive
The Ultra 4 sibling to the same-day Series 12 hands-on, shot at Apple Park in the same session — and it carries the mechanism the Series 12 video left out: the LED array has been rearranged so the color diodes are now clustered by type (four green, four red, four infrared), which lets Apple drive 24/7 background readings off the green LEDs instead of the infrared ones. That's why background HR could go from every 5 minutes to every 5 seconds; it's an LED-grouping change, not just a faster sample loop.