Besides using Portrait Mode, what is a key physical technique involving subject-to-background distance and lens choice to maximize the shallow depth of field effect when capturing a photo or video with an iPhone?

Shallow depth of field refers to the photographic effect where a very small portion of the image, typically the main subject, appears sharp and in focus, while the areas in front of and behind the subject are increasingly blurred. This selective focus draws attention to the subject by isolating it from its surroundings. To maximize this shallow depth of field effect on an iPhone without using Portrait Mode, a key physical technique involves two main adjustments: subject-to-camera distance and subject-to-background distance, combined with a specific lens choice. First, physically move the iPhone as close as possible to the subject. This minimized camera-to-subject distance inherently makes the depth of field shallower, rendering the subject sharp while progressively blurring elements closer to and further from it. Second, simultaneously ensure there is a significant distance between the subject and its background. A greater subject-to-background separation allows the out-of-focus background elements to appear more blurred and less defined, which visually enhances the perception of a shallow depth of field. Complementing these distance adjustments, the choice of lens is crucial. Select the telephoto lens option available on the iPhone, typically represented as 2x, 3x, or 5x in the camera interface. A telephoto lens is characterized by its longer focal length compared to the standard wide (1x) or ultra-wide (0.5x) lenses. Longer focal lengths inherently produce a shallower depth of field at a given aperture and subject distance, resulting in a more pronounced background blur and effectively isolating the subject.