The iPhone 18 Pro is the first iPhone to feature a variable aperture, one of the headlining features of this year's Pro models. Adjustable apertures have long been an essential tool for photographers using professional and prosumer camera systems, and their absence from mobile cameras has become more noticeable as other smartphone features have advanced. A handful of phones have offered variable aperture on their main cameras over the years, but the feature never caught on, as most manufacturers abandoned it in favor of the fixed-aperture systems that phone cameras have traditionally used.
It could be that the iPhone's adoption will finally bring the feature into the mainstream. Still, variable aperture may be technical enough that many owners won't know how it works or even that it exists, which would be a shame, since it enables some useful creative control. Here is a primer on a technique photographers and cinematographers have relied on for decades.
Aperture simply refers to an opening. On a camera or lens, it is the opening through which light enters the system and reaches the image sensor. A variable aperture lets you control the diameter of that opening, and therefore how much light gets in. The mechanism usually relies on a ring of blades that move in or out, either electronically with motors or mechanically on certain lenses. The principle mirrors the human iris, which widens in the dark and narrows in bright light.
Aperture size is expressed as an F-number or F-stop, the ratio of the lens's focal length to the aperture diameter, which is why values such as f/1.8, f/2.5 and f/11 appear. Because it is a ratio, a smaller number means a larger opening, and identical values allow comparison across different camera systems. Aperture is one of four main ways to control light capture, alongside shutter speed, ISO and physical filters, the latter two of which are discussed next.
Source: GSMArena · Summarized by HeadlinesBriefing