SUMMARY
The variable aperture on the iPhone 18 Pro, ranging from f/1.48 to f/4, has sparked debate, with many arguing it's a video enhancement rather than a photo capability. The device's small sensor size and densely packed photosites limit its ability to achieve shallow depth of field like full-frame cameras. Diffraction also prevents the aperture from stopping down beyond f/4 without significant image degradation. While exposure settings are universal, the resulting image 'look' differs greatly due to sensor size, making the variable aperture more beneficial for achieving natural motion blur in video.
TAKEAWAYS
iPhone 18 Pro's variable aperture is mainly for video, not photo depth of field.
Small sensor size and dense photosites prevent shallow depth of field.
Diffraction limits the aperture to f/4 to maintain image sharpness.
Variable aperture aids in achieving natural motion blur for video.