Remember two years ago when OnePlus had to explain that the OnePlus 5 phone it had just launched didn’t really have true 2x optical zoom like the company said? Well, it happened again. The OnePlus 7 Pro now comes with 3x optical zoom on paper, which is an impressive feat for a mobile phone. But before you get too excited, you should know that it’s not quite the 3x zoom you thought you’re getting.

A Redditor was first to observe that the OnePlus 7 Pro’s telephoto lens doesn’t actually do 3x optical zoom, which is what OnePlus advertised. By comparing regular photos taken with the telephoto lens and then switching to portrait mode, the user discovered that the picture is less zoomed in portrait mode — here’s an example.

The person also looked at EXIF data for the pictures, as well as the hardware, and concluded that the OnePlus 7 Pro has real optical zoom of 2.2x rather than 3x.

In practice, what this means is that you’ll get 13-megapixel portrait photos but only 8-megapixel shots in “3x optical zoom” mode, even though the exact same lens and sensor are used each time. Here’s an explanation from Android Police, which also looked into the matter:

Both modes use the same lens and sensor, but somehow the image produced in Portrait mode is of a wider angle and at a higher resolution — 13MP in Portrait mode compared to 8MP in 3x “zoom” mode. So, in fact, the telephoto lens has a higher 13MP resolution, and it’s actually cropping down to hit that 3x zoom target.

Based on the math which describes the geometry of the situation, that crop places the actual optics of the telephoto lens around 2.2x rather than 3x (or 57mm instead of 78mm, in focal length and 35mm-equivalent terms).

OnePlus responded to the confusion, maintaining that the phone has 3x zoom:

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.

Marketing the phone as having 3x zoom seems a bit off, as OnePlus should have explained these matters from the get-go. Pro photographers and even amateurs who are familiar with the physics would have discovered these inconsistencies, as this Redditor just proved. You can read the post in full below: