The iPhone 18 Pro has three rear cameras, but only the main camera offers a variable aperture. It's a 48-megapixel sensor with four aperture f-numbers supported. You can pick an aperture value from f/1.48, f/1.8, f/2.8, and f/4.0m, which should make it significantly easier to get the exposure just right in difficult lighting conditions. You'll also be able to take better photos in low light and try a few additional creative shots with your iPhone 18 Pro. Having a variable aperture is great for controlling depth of field, so you can easily blur the background or keep it in sharp focus when you take photos.

With a larger aperture (f/1.48), you'll be able to reduce the depth of field and blur the background for shots that require focus on a single subject. You can use a smaller aperture (f/4.0) to capture stunning landscapes, where you want the entire photo to be in focus.

https://lifehacker.com/tech/iphone-18-pro-variable-aperture-explained