New Delhi, Oct. 12 -- Reading a route or pace field halfway through a sunny run is the practical problem COROS is trying to solve with the PACE 4 Pro. Its largest watch display pairs a bright AMOLED panel with a narrow titanium bezel and sapphire glass. The catch is not whether the screen exists, but how its brightness, always-on setting and GPS mode change the battery figures attached to it.

COROS lists a 1.47-inch touchscreen with 466 by 466 resolution and a peak brightness of 3,500 nits on its product page. The company calls it its biggest and brightest watch screen. That places the emphasis on visibility and room for maps, a different question from simply joining the wider push for brighter smartwatch displays. Peak output is a maxim...