One example of the aforementioned CyanogenMod goodness: You can adjust screen brightness by swiping left or right along the omnipresent status bar. Another: Double-tapping the screen wakes the phone (a nice workaround for that hard-to-find power button) and drawing a "V" -- even when the screen is off -- toggles the dual-LED flashlight.
Those LEDs also provide the lighting for the One's rear camera: the impressive-sounding Sony Exmor IMX214 with f/2.0 aperture. It employs a 13-megapixel sensor and those dual LEDs promise extra lighting in dark environments -- though it's not as sophisticated as the iPhone 5s' True Tone system, so the camera is really just blasting extra light (usually to the subjects' detriment).
The front camera does a better-than-average job snapping selfies thanks to its wide-angle lens, which captures a wider field of view than, say, my iPhone 5s.
As for video, the One can capture not only 1080p, but also ultra-high definition (UHD -- also known as 4K and 2160p). It offers a 120fps slow-motion mode as well, though this requires you to downshift from 1080p to 720p -- a fact you discover only after trying to record at 1080p, at which you're limited to 60fps. (OnePlus needs to tweak the software so you can't select 120fps if you've also selected 1080p.)
The CyanogenMod Camera app is a joy to use, with clear onscreen controls and plenty of scene modes. You can select one of the latter via a typical menu, but it also lets you swipe up and down in the viewfinder to quickly "dial" through the available modes. That's so much faster than venturing into a menu over and over again until you find a scene setting you like.
After shooting in a variety of low-light and indoor/outdoor settings, I can attest that, while colors felt a bit muted and exposure wasn't always consistent, overall, the camera performed admirably. Low-light shots in particular were nearly as good as those captured with an iPhone 5s, and 120fps video -- even at the lower resolution -- looked silky-smooth. I'm fairly forgiving when it comes to smartphone photography, coveting convenience and versatility over perfect color accuracy, and I had few complaints with the One's camera.
In fact, the only real downside I discovered was a lengthy shutter lag (1-2 seconds, I'd say) when shooting in low light with the flash enabled.
The OnePlus One is as fast and responsive as any phone I've used. Apps loaded anywhere between instantly and quickly, though that's hardly the most telling indicator of performance. My preferred informal test is to run about a dozen apps simultaneously, then fire up the browser and see if there's any lag when I zoom in or out. Here, there was zero: The screen immediately snapped to whatever size I chose.
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