One of the major features of the OnePlus 7 Pro is its triple rear camera setup, which includes a 3x optical zoom camera according to OnePlus. However, it turns out that that camera may not actually offer 3x optical zoom.
The telephoto camera on the OnePlus 7 Pro is actually around a 2.2x optical zoom. That's according to Reddit user ImKuya and Android Police, who did some sleuthing to discover that the telephoto camera actually takes 13MP photos in Portrait Mode (which uses the telephoto camera) but 8MP images in 3x zoom mode. These reports note that when you're taking a photo with Portrait Mode and the telephoto camera, you're getting a wider field of view than you do with the 3x zoom in the normal Photo mode.
What's happening is that OnePlus is cropping out the edges of the photo down to get that 8MP 3x zoom image. So instead of the 78mm focal length you'd expect from the 3x optical zoom camera, you're getting 57mm and around 2.2x optical zoom.
The other thing that's notable about this situation is that it's not the first time that there have been questions about the zoom capabilities of a OnePlus phone's camera. The OnePlus 5 was first said to have a 2x optical zoom, but it was found that the phone actually only offers a 1.6x optical zoom, with the other 0.4x achieved using SmartCapture digital zoom.
Optical zoom is at 1.6x, the remaining 0.4x is realized through SmartCapture multiframe technology.
— Carl Pei (@getpeid) June 21, 2017
Most OnePlus 7 Pro owners likely won't notice that the telephoto camera doesn't quite offer 3x optical zoom, but it's still something to keep in mind about the new flagship. OnePlus specifically advertises the OP7 Pro's telephoto camera as offering "3x optical zoom", and so it'll be interesting to hear what the company has to say about this development.
UPDATE: Here's OnePlus's statement to Android Police on the matter:
"The OnePlus 7 Pro has 3x zoom with no digital zoom or loss of detail. The telephoto camera serves two main purposes: 3x zoom and portrait mode photography. It will switch the field of view depending on the camera mode. With 3x zoom, the telephoto camera delivers the advertised lossless 8 megapixels images. Portrait mode utilizes all 13 megapixels from the sensor in the telephoto camera."