The iPhone 18 Pro is the first iPhone model to feature a variable aperture, a headlining feature for this year's Pro models. An adjustable aperture has been an invaluable tool for photographers on professional and prosumer camera systems, and its absence from mobile cameras has become increasingly conspicuous as everything else on these devices has leveled up.
There have been a handful of phones over the years that featured a variable aperture system for their main camera. However, the feature never stuck around long enough to enter the lexicon of the average smartphone user, as most manufacturers who experimented with it abandoned it shortly after in favor of the fixed-aperture systems phone cameras have traditionally used.
There is an argument to be made that the iPhone getting a feature might be the quickest way for it to enter the mainstream consciousness. However, variable aperture for the camera might just be nerdy enough that people who have it on their phone might not know how it works or even that it exists. Which would be a shame, as you could do some cool things with it.
So here's something that will get you up to speed on a technique photographers and cinematographers have relied upon for decades to get the perfect shot, and how you can get the most out of that new iPhone 18 Pro that you just purchased.
But first…
What is variable aperture? Actually, what even is aperture?
Aperture is a common photographic term, but English speakers would know that the word simply means a hole or an opening. An aperture on a camera or a lens is the opening through which light enters the camera system and exposes the film or the image sensor. A variable aperture is one where you control the diameter of the aperture and thus the amount of light entering the system.
Image source: iFixit iPhone 18 Pro teardown
The aperture system usually works by having a ring of blades that move in or out to adjust the size of the opening, and this can be done electronically with motors or mechanically on certain camera lenses. This adjusts the diameter of the aperture, the same way the iris of the eye expands or contracts to adjust the size of the pupil. The principle is the same; the aperture gets wider to let more light in when it's dark and narrower when it's bright.
The aperture size is not typically stated in conventional distance units but rather as a ratio between the lens's focal length and the diameter of the aperture, in a value known as the F-number or the F-stop. This is why aperture sizes are traditionally found written as f/1.8, f/2.5, f/11, etc., and since they are ratios, the smaller the number, the bigger the actual aperture diameter is. It also allows the numbers to be comparable across different camera systems, as f/2.8 on one system will allow the same amount of light in as f/2.8 on a different camera system, with different sensor and lens sizes.
However, aperture is only one of the four main ways you can adjust the light capture of your camera; the other three being shutter speed, ISO, and a physical filter over the lens. For the time being, we will ignore filters — even though they are certainly an option for iPhones — and focus on the other two.
The shutter speed of the camera is how long the film or the image sensor is exposed to light. Typically, the shutter is only open for a fraction of a second, so you'll see it being written as 1/250 or 1/8, which is a measure of how much of a second it's open for. For smartphone cameras without a mechanical shutter, the sensor is technically always exposed to light (which is also how the viewfinder works), so the shutter speed instead denotes the time for which it is actively exposing for the image. A longer shutter speed allows more light to be captured, but increases motion blur in case the camera or the subject moves. On the other hand, reducing the shutter speed to capture a perfectly still image will create a darker image, with everything else being equal.
ISO (pronounced aye-sow) tells you the sensitivity of the image sensor. Back in the day, ISO value denoted the light sensitivity of the photographic film, but in the digital world it refers more to how much gain is being applied to the sensor. The image sensor has a base native ISO, optimized for the best signal-to-noise ratio. By boosting the ISO value, you increase the gain, which indiscriminately increases both the signal and the noise. This is why increasing ISO does make the image brighter, but also increases the noise in the image.
ISO is usually denoted in values like ISO 80, ISO 160, ISO 320, etc., with the lowest number usually being the base ISO. The numbers don't mean much themselves but rather tell you how much the sensitivity has increased relative to each other. So ISO 200 means it's twice as sensitive as ISO 100.
The reason for this digression is that aperture is part of a three-way dance between it, shutter speed, and ISO that the camera has to do each time to expose the shot correctly. Understanding and utilizing aperture settings requires understanding how it relates to shutter speed and ISO, and how they affect each other.
Now, let's look at what controlling aperture on your iPhone 18 Pro, or any camera with this option, can do.
Motion
One of the critical factors for deciding the look of a video is how motion appears in it, and it's decided primarily by the frame rate and shutter speed. There is an established relationship between them, defined by the 180-degree shutter rule that cinematographers typically follow. According to the rule, the denominator of your shutter speed should typically be twice the number of your frame rate, so for 24fps, you should ideally use 1/48 or 1/50 shutter speed, whichever is available.
However, picking this ideal shutter speed for video isn't always feasible, as depending on the light, it could make the video too bright. This is where other things like ISO, filters, and, of course, aperture come in. With an adjustable aperture, you can reduce the amount of light hitting the sensor, and thus maintain your ideal shutter speed.
First, let's look at this sample clip, where a moving object is first shot with a high shutter speed and later with a more appropriate shutter speed. You can see how the motion in the first segment is jittery, typical of smartphone-shot footage, while the second one looks much more natural and, dare I say (for a clip of a fidget spinner), cinematic.
Seeing still frames from both shots shows this more clearly. The difference between the two is that the first is shot with an f/1.46 aperture and a short shutter speed, and the second with f/4 and a longer shutter speed. With the aperture narrowed, the phone automatically picked a longer shutter speed to compensate, creating smoother motion. In other words, the difference in motion is coming from the shutter speed being different as a result of the aperture, and not due to the aperture itself.
f/1.46 • f/4
Unlike photos, you want some motion blur in videos for a more natural look, which is why films, despite their relatively low 24fps frame rate, tend to look so smooth and natural. The jittery, high shutter speed video looks very unnatural, but it has been the norm for smartphone videos shot in bright lighting, as the only knobs they could adjust in the past were shutter speed and ISO to maintain exposure. But when you throw variable aperture into the mix, there is now another knob for you or the phone to adjust. Unlike shutter speed, aperture does not have any direct effect on how motion appears in the shot, so you can turn it down instead of shutter speed to get your desired look, and still maintain correct exposure.
Of course, in very bright lighting, you'd still need to use a neutral density or ND filter, which further blocks harsh light from overwhelming the sensor and lets you keep both your shutter speed and aperture values for the intended look. However, that's only for serious shoots and super bright scenarios, and in most cases now, you can get away with just making the aperture smaller on the iPhone 18 Pro.
Bottom line: You can pick smaller aperture sizes and use slower shutter speeds to get smoother, more cinematic videos without overexposing them.
Depth of field
Depth of field is the space around the plane of focus, within which things remain in focus. A shallow depth of field will cause anything immediately behind or ahead of the plane of focus to remain unfocused. On the other hand, a deeper depth of field allows more objects ahead and behind to remain in focus. A shallow depth of field can be more pleasing but can severely constrict the area of focus around the subject. A deeper depth of field may not look as nice but is more practical for keeping more of the subject in focus.
Image source: 1st Vision
Depth of field is affected by the distance of the subject to the camera, focal length, sensor size, and yes, aperture. With all else being the same, changing the aperture size lets you capture the same overall frame, but the angle at which light enters the camera changes dramatically. A wider aperture makes light enter at broader angles, thereby vastly constricting the depth of field and requiring more precise focus. A narrower aperture causes light to enter at shallower angles, stretching out the depth of field and making it easier to focus.
f/1.46 • f/1.8 • f/2.8 • f/4
This one is a bit obvious, but it's still worth showing it in action on the iPhone 18 Pro. The main camera doesn't have the closest focusing distance to show this effectively, but you can still see it well enough in these samples. In the first set, you can see how very little of the can is in focus at f/1.46, but it gets gradually sharper as the focus plane expands and covers more area. This set also shows why the iPhone 18 Pro defaults to f/1.8 for most shots, as f/1.46 can be very soft for close-ups due to its minuscule focusing plane.
f/1.46 • f/1.8 • f/2.8 • f/4
This is another area where dialing a setting down instead of up can be the recommended option. A shallow depth of field can look cool, but not if half of the subject is out of focus, and you can't even tell what part is in focus anymore. Phone cameras have had this happening to them for a while now as sensor and aperture sizes both keep getting larger in unison, and close-up shots essentially have 2mm of the subject in focus with heavy fringing around it. Manual aperture control can provide some relief in this instance.
Bottom line: You can pick smaller apertures for better detail and less fringing on close-up shots, or larger apertures for shallower depth of field and better background separation.
Detail
One downside of a wide aperture and the resulting shallower depth of field is that the image as a whole can get softer. Landscape photographers know that for maximum sharpness, you don't go for the maximum aperture size, but rather head in the other direction and stop it down aggressively.
A good thing about variable aperture on a phone is not just that you can make it wider, but more importantly, smaller. This can, in theory, make the image sharper and get more out of the resolution of the sensor.
Image Detail: f/1.46 vs. f/4
In practice, things didn't change dramatically on the iPhone 18 Pro while shooting on either end of the aperture spectrum, and comparing images shot at f/1.46 and f/4 felt like splitting hairs, as the differences were minimal. We even shot the images in RAW before exporting them to JPEG in Lightroom to avoid the iPhone software potentially compensating for the different apertures. At best, the f/4 image had better corner sharpness (where you'd notice the differences anyway) and less purple fringing around high-contrast subjects. On the other hand, they also exhibited starburst patterns around bright specular highlights, as is typical of small apertures with fewer blades.
This means you can choose the smaller aperture sizes if you value maximum corner-to-corner sharpness in your images, especially when shooting in RAW at full 48MP resolution. However, if light levels aren't sufficient, or if the starburst pattern isn't desirable, you can get away with shooting in the wider apertures without losing a meaningful amount of detail.
Bottom line: You can pick smaller apertures for slightly more detail while shooting landscapes at higher resolutions.
Exposure
The most obvious use of aperture control is adjusting the amount of light captured by the camera. It's also the least interesting or meaningful use for it.
Adjusting aperture simply to make the image brighter or darker isn't a particularly good use for the feature on the iPhone 18 Pro. For one, there doesn't seem to make much sense to reduce the light coming in if it's not for one of the aforementioned reasons. You'll always be better off with a wider aperture in that case, which is why most phones just ship with a wide aperture by default.
Second, the 18 Pro aperture can go wider than previous iPhones (f/1.46 vs f/1.8), but the difference usually isn't massive for light levels. The reason for that is that the software can deftly control ISO and shutter speed values to compensate. Moreover, unlike regular cameras, smartphones like the iPhone have night mode, which takes long exposures and stacks multiple images to further improve image quality in low light. So in practice, you never really have to mess with the aperture setting for this specific purpose.
f/1.46 • f/1.8 • f/2.8 • f/4
The images above were captured with the four available aperture settings to demonstrate the difference. To make the difference actually visible, the shutter speed was locked and the night mode was manually disabled. The quality is obviously bad, but this way, you can see a difference between the four aperture sizes; in typical usage, this difference won't be as obvious.
As an aside, the iPhone Camera app exposes only four aperture values of f/1.46, f/1.8, f/2.8, and f/4. However, that doesn't mean the variable aperture system is limited to those values. Third-party camera apps like Optika have as many as nine different aperture settings available, all of which offer much more fine-grained control over the aperture blades. Having to download a third-party app to get full control over the hardware doesn't feel great. But then again, you probably should, because the iPhone Camera app still doesn't offer ISO control, which you get in other apps, and it significantly improves your control over the photographic process.
Bottom line: The larger apertures can be brighter and have less noise, but the phone will do this automatically anyway so you don't need to bother with it.
Verdict
The variable aperture feature on the iPhone 18 Pro may not be new or revolutionary. However, it can still be a useful tool in your arsenal if you know how to use it, which hopefully you now do if you made it this far into the article. The times where it is at its most effective, it can make a substantial difference to how things look, and videographers will especially appreciate how much nicer it can make motion appear in their shots without having to reach for their NDs.
It's also yet another thing for users to experiment and learn with, which is never a bad thing. This could very well be how you learn how photography on proper cameras works, and decide to get into the hobby.
Having said that, there are a few things Apple can improve to make things better for everyone. For one, the variable aperture feature is only available on the main camera on the 18 Pro, which is a bummer. At the very least, the telephoto camera also deserves to get this feature, which we hope happens in the future.
Second, the iPhone Camera app UI is starting to get increasingly cluttered; Apple keeps adding more camera options, which is a good thing, but the features sort of just all get lumped together into a single menu, which is starting to get rather long and makes sorting the useful stuff from the non-essential stuff hard. You also have to go back and forth through the menu to adjust different settings, and the quick toggles only become available once a setting has been changed, and disappear once it goes back to default. What the iPhone Camera app needs desperately is a Pro mode with all the relevant options on a separate screen so it stops being cumbersome to serious photographers and overwhelming to casual users.
That aside, it was fun to experiment with this feature on the iPhone 18 Pro, and hopefully Apple keeps it around and improves upon it on future models. We also hope other manufacturers bring this feature back, at least on their flagship devices, as it's always nice to have more options available for consumers.
Apple iPhone 18 Pro
| 256GB 12GB RAM | € 1,449.00 | £ 1,199.00 |
| 512GB 12GB RAM | € 1,699.00 | £ 1,399.00 |
| Show all prices |