The Real Truth Behind the iPhone 18 Pro's New Variable Aperture

While unveiling the iPhone 18 Pro , Apple highlighted a cool new camera feature—variable aperture. It's uncommon among smartphones , though not a first, and will come in handy for some types of photos. Of course, in its typical fashion, Apple delivered news of the upgrade from within its reality distortion field to maximize hype. I've been reviewing cameras for more than 15 years, so I'm here to explain what variable aperture is, why you'd want it, and when you'll still need an add-on filter to reduce the amount of light entering the lens.

The Basics: How Aperture Controls Light and Focus

If you've only ever used a smartphone for photography, you're used to lenses that work at one and only one aperture, also called f-stop. In plain language, the aperture is a numerical value that indicates how much light a lens lets in and projects onto a digital image sensor. Phones tend to use wide-aperture lenses that let in as much light as possible to capture good photos in tough light, and default to very short shutter speeds when taking photos or videos out in the sun. The main lens of the iPhone 17 Pro has an f/1.78 aperture, which is considered quite bright and ideal for taking photos in dimly lit environments.

A variable aperture uses a set of blades that close down from the sides to block some of the incoming light. Getting less light into the system lets you more easily use longer shutter speeds to introduce some motion blur, and increases the depth of field, the fancy technical term for how much of a scene is in sharp focus. One bit of housekeeping: Apertures are expressed in fractions, so a smaller number means that more light is coming in.

One Lens Only: The Fine Print

The iPhone 18 Pro's main lens is rated for f/1.48, which means that when it's used with the aperture wide open, it is more sensitive to light than the 17 Pro's f/1.78 lens. But instead of being stuck wide open like the 17 Pro, the 18 Pro includes a six-blade diaphragm that closes down to f/1.8, f/2.8, or f/4.0.

The iPhone 18 Pro adds a variable aperture to its main lens and redesigns its optics to gather more light. When used with the Camera app in automatic mode, the f-stop changes automatically based on the light. If you're taking photos in a dimly lit interior, it'll open to f/1.48 to let in as much light as possible. For beach days and sunny landscapes, the phone will narrow the diaphragm to reduce light.

One note: The variable aperture is only included in the main 24mm wide-angle lens; it's not available on the ultra-wide (13mm) or telephoto (100mm) lenses. Those are unchanged from the iPhone 17 Pro.

Unlocking Creative Exposure With Pro Controls

You don't have to be stuck with automatic adjustments, however. Apple includes manual exposure settings, called Pro Controls, for both photography and video. These let you adjust various aspects of your exposure, including shutter speed, aperture, and white balance. Knowledgeable photographers can use manual settings, along with the variable aperture, to take more creative control over their pictures.

There are two main reasons to use a small aperture. The first is depth of field. The iPhone 18 Pro's f/1.48 lens and Type 1 image sensor will be able to create some optical blur in the right situation. iPhone photographers are used to having to go into Portrait mode and use depth mapping to blur backgrounds, but given the physics behind the 18 Pro's camera system, it will achieve similar effects when the camera is positioned close to a subject and there is some distance between it and the background or foreground.

I don't anticipate the iPhone 18 Pro giving you the soft-background bokeh look without portrait mode in many situations, even when the lens opens all the way to f/1.48. Once you put enough distance between the camera and the subject, everything is in focus from an optical standpoint. Using f/2.8 or f/4 may result in slightly sharper backgrounds, but not enough to notice on a 6-inch phone screen or in a social media post.

Now, sunstars are another matter. Apple showed off the iPhone 18 Pro's ability to produce bright highlights with dramatic spikes. That's something that happens optically, not computationally. When light passes through an aperture, it takes on its shape, and narrower f-stops can make light particles scatter, an effect called diffraction. These diffraction spikes, commonly called sunstars in the photo world, can add drama to landscapes, cityscapes, and portraits. You won't see them in every photo, but they're easy to get if you catch a bright reflection off a piece of jewelry, bits of sunlight peeking through leaves, or sunlight on the surface of water.

The Physical Limits: Why You Still Need an ND Filter

The second reason to cut incoming light is to achieve long-exposure effects. I like to use a half-second shutter speed to smooth out flowing water for landscape photos that include streams and waterfalls, and I will go even longer for urban landscapes where I want to blur out pedestrians and cars. Videographers will try for what's called a 180-degree shutter angle to record motion with just a touch of blur, an effect that reads as more cinematic. To get this angle, you want to set your shutter speed to half of your frame rate—1/48-second for 24fps, 1/60-second for 30fps, and so on.

For interiors, night scenes, and twilight, the f/1.48-4.0 aperture range will give you enough leeway for photos that intentionally blur motion and cinematic shutter angles, but it's likely to fall short under sunny skies. You'll still want to add a neutral density (ND) filter over the lens if you want to get some motion blur in bright light.

I'm surprised that Apple didn't add computational tricks to boost its variable-aperture lens in these types of scenes. Granted, I haven't tested the phone yet, so it could simply be something Apple chose not to mention.

Is Variable Aperture Worth the Hype?

I plan to test the limits of the iPhone 18 Pro's camera for long exposures and other creative shots as soon as possible. On the surface, variable aperture feels like a nice addition, but it's far from a game-changer. If you're a casual snapper who just wants to capture moments with your phone, you won't ever have to think about the aperture. Apple's Camera app will decide where to set it, and you'll still want to use Portrait mode for a blurred background, because in most situations, optical blur won't deliver the bokeh look.

Knowledgeable photographers and videographers will get more mileage from the f/1.48-4.0 adjustment range and should be savvy enough to recognize its limitations. If you're in this group, you'll still want to add a neutral density filter. And don't worry, you'll have the option if you want—as I write this, the iPhone has been public for all of 90 minutes, and I've already received an email from Moment, one of the biggest makers of photo and video accessories for smartphones, letting me know that it has an adjustable Variable ND filter ready for the iPhone 18 Pro. Apple's latest killer feature isn't enough to kill the accessory market.

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