Distortion, or the lack there-of. One of the surprising things about the Sirui 18mm lens on the iPhone SE2020 and the Moment thin case is how little distortion there is both across the field and at the edges of the field. If you have used other wide angle add-on lenses for your phone, or even the native wide angle lens if you phone is equipped with one, you know that this level of quality is the exception, not the rule. This shot did require some “vertical perspective” correction in Polarr as the 18mm perspective tips verticals back toward the horizon if you have the camera pointing up at all, as in this case, to catch more of the sky drama…but that is just something all lenses do whenever the sensor is not perpendicular to the horizon. It is so common in photographs that we generally do not even see it. Architectural photographers, who care about such things, use special lenses which eliminate the vertical tilt. It can also be corrected in many photo editing apps. iPhone SE2020 with the Moment thin case and the Sirui 18mm lens. Native camera app on Auto.