Test Finds iPhone 18 Pro's Wider f/1.48 Aperture Improves Background Blur, With Limits

Apple has promoted the iPhone 18 Pro’s variable aperture and wider opening as enabling a shallower depth of field for portraits and similar shots. According to 9to5Mac, the change amounts to less than a full stop, leaving it unclear how much practical difference it would make on a small sensor. The site set out to test that question using the phone’s new manual aperture controls.

The test drew a distinction between optical background blur and the artificial effect produced by Portrait mode. Portrait mode uses computational photography and the LiDAR sensor to determine where the subject ends and the background begins, then applies an artificial blur. The sample photos in the 9to5Mac test used only optical blur, shot at the widest possible aperture of f/1.48.

To isolate the effect of aperture, the site compared the iPhone 18 Pro’s f/1.48 setting with f/1.8, which is the second-widest aperture available on that phone and essentially indistinguishable from the iPhone 17 Pro’s widest f/1.78 setting. Using the same main camera, the same framing and the same distance to the subject, the photographer took the same photo twice and changed only the aperture. A few seconds passed between shots while the aperture was adjusted, but both the photographer and the subject stood still to keep the distance consistent.

The test shots were head-and-shoulder portraits, a type of photo for which wide apertures are most commonly used. The close framing also maximized expected background blur, making it easier to compare the two apertures. Some shots included backgrounds that receded gradually with distance.

In one image containing background elements from a few feet to roughly a quarter of a mile away, the fountain closest to the subject, at about 8 to 10 feet, showed a noticeable difference between the two apertures. A tree about 30 feet away showed a smaller but still distinct difference. A pagoda about 70 feet away showed a clear but less pronounced difference. For more distant elements, such as a bridge and buildings on the far side of a river, the difference became subtle; 9to5Mac said it was visible when actively looking for it, but most people would not notice it unprompted.

A second example illustrated the practical benefit. At f/1.78, the separation between the subject, Chris, and the background was described as marginal in places, including a person eating in a restaurant at the top right and part of a building above his head. With the wider aperture, that separation improved.

9to5Mac described the overall difference as relatively subtle but bigger than expected, and enough to be useful in some situations. The site also noted that the wider aperture is not the only benefit of the new lens, and said it would examine other uses for manual control of the variable aperture in a follow-up piece.