The OnePlus 7 Pro is undoubtedly a great phone with a class-leading 90Hz QHD+ AMOLED display, fast performance thanks to the Qualcomm Snapdragon 855, and a near bezel-less display thanks to the use of a popup camera. However, it's not free from its share of issues. The triple rear camera setup hasn't quite lived up to OnePlus' promises so far, high DxOMark score notwithstanding. Our full camera review will be published after evaluating OnePlus' upcoming camera update, but as of now, the cameras deliver regrettably average image quality, although they provide a lot of flexibility with a standard + ultra-wide + telephoto lens setup. Now, Reddit user /u/ImKuya has discovered a few characteristics of the OnePlus 7 Pro's telephoto lens that point to misleading marketing from OnePlus. The company has now issued a statement on the matter, which can be read at the end of this article.
At launch, the OnePlus 7 Pro was promoted as having an 8MP telephoto camera with 3x optical zoom. The reviewers' guide for the phone even mentions that the telephoto camera has a 78mm focal length in 35mm equivalent terms. As discovered by the Reddit user, this is not the case. The camera is actually a 13MP Samsung S5K3M5 sensor with a native 57mm focal length. As the focal length of the OnePlus 7 Pro's primary 48MP camera is 26mm, 57mm is closer to 2.2x optical zoom than 3x optical zoom. This makes it clear that OnePlus' original marketing material was incorrect and disingenuous on this subject.
The 13MP telephoto camera is used to take portrait photos. In itself, there is nothing odd in this. Photos are taken at the full 13MP resolution (4160x3120) without any cropping. The interesting thing is when portrait mode photos are compared with the main telephoto camera mode, which enables users to take standard photos with the telephoto camera. These photos are taken with 8MP resolution (3264x2448), and not 13MP. They also have a narrower field-of-view (FOV) than the portrait mode photos, signifying that OnePlus is cropping the 13MP sensor to result in 8MP photos that have 3x zoom relative to the primary camera.
Now, is this 3x zoom optical or digital? The answer is that it's neither optical nor digital. It can't be optical because the focal length of the sensor is 57mm. OnePlus is achieving the 78mm figure by cropping in, but the results won't be the same in terms of perspective and geometry. Objects such as faces look different at different focal lengths. At the same time, the 3x zoom is also not digital because the company is still using the native data from the 13MP 2.2x zoom image. OnePlus is trading off resolution in order to get the 3x zoom figure. In the company's statement (see below), this zoom is now referred to as 3x "lossless" zoom.
Users expecting a full native 78mm focal length from the OnePlus 7 Pro's telephoto lens, will, therefore, be disappointed. A 57mm crop will not magically result in 78mm with cropping, even though the differences will be minor to all but the most discerning users. Case in point: I didn't become aware of this characteristic on my own.
The problem is with OnePlus' marketing. The original marketing material specifically proclaimed 3x optical zoom, and this is false. The camera can only do 2.2x optical zoom, with the remaining amount (0.8x) being achieved by cropping. The whole situation is eerily similar to the OnePlus 5. The OnePlus 5 is ironically enough the only other OnePlus phone to feature a telephoto lens prior to the OnePlus 7 Pro. Its 20MP secondary camera had a 40mm "telephoto" lens. After first proclaiming that it could do 2x optical zoom, OnePlus later clarified that it could only do 1.6x optical zoom, with the remaining amount being achieved by OnePlus' SmartCapture (digital interpolation).
OnePlus' statement regarding the OnePlus 7 Pro's telephoto lens
OnePlus later provided the following statement to Android Police:
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.
The takeaway
The OnePlus 7 Pro's telephoto camera has 13MP native resolution with a 57mm equivalent focal length. This means that it provides 2.2x optical zoom relative to the primary camera, and not 3x. In the telephoto camera mode, OnePlus uses cropping to produce 8MP photos with magnification to provide 3x lossless zoom. Discerning users will be able to note the differences between a native 78mm focal length lens and a cropped image from a 57mm focal length lens, but the differences will be related to perspective. Differences in image quality are expected to be minor, but they are still there.
This is where we have to clarify one thing: Smartphones are not interchangeable lens cameras. A phone with a camera that has 3x optical zoom means that it can switch to a camera that has a focal length of three times the magnification relative to the primary camera. 3x optical zoom in a telephoto doesn't mean that 2x zoom, for example, will be optical. Smartphone cameras have fixed focal lengths, a constraint that differentiates them versus DSLRs and mirrorless cameras. We will go into much more detail in an upcoming "camera terminology explained" article, so stay tuned.