Is the iPhone 18 Pro’s variable aperture any good?
The new iPhone has a feature you’d ordinarily see on a high-end camera. While it doesn’t live up to Apple’s lofty promises, it does have its advantages.
Testing the iPhone 18 Pro’s most-hyped feature
But is there any truth to these salesy promises? In a bid to find out, I put the feature under the microscope – and got a mixed first impression. In most situations, the variable aperture makes zero difference to your photos. But that doesn’t mean it’s entirely pointless.
Very little control over depth of field
If you’re a photography buff, you’ll be familiar with the concept of a variable aperture from using traditional cameras. It’s a mechanism that uses multiple blades to increase or decrease the size of the lens opening. On larger cameras, variable apertures are indispensable because they serve two important functions:
- Controlling light intake: If you’re taking pictures in blazing sunlight, a fully open lens lets in so much light that the camera’s shutter can’t expose the sensor for a short enough period of time. As a result, photos turn out overexposed. A variable aperture solves that problem.
- Controlling depth of field: The larger the lens opening, the smaller the area in focus. Photographers often want this, as it means the subject in focus stands out from the background. It’s a technique used in portrait photography, for instance. In other scenarios, however, every area of the photo needs to be equally sharp. Landscape photography is a prime example of this. Variable apertures allow you to control that depth of field.
On a smartphone, these functions are mostly unnecessary. This is down to the device’s tiny image sensor (1/12 of the size of a full-frame sensor) and its electronic shutter. It already achieves high enough shutter speeds – even in direct sunlight with the lens wide open. As a result, you don’t need a variable aperture to get proper exposure.
The small sensor also means that the focal plane is super wide anyway – especially with a wide-angle lens like the one on the iPhone’s main camera (24 mm 35 mm equivalent). The maximum aperture of ƒ/1.48 produces roughly the same depth of field as ƒ/5.2 on a full-frame camera. Photos come out pretty sharp all over, unless you get extremely close to the subject. The new aperture can only make the focal plane larger, not smaller. That means pronounced blurring (known as «bokeh») still has to be created digitally using Portrait Mode.
Strictly speaking, the «more control over exposure and depth of field» promised in Apple’s promotional materials isn’t a lie. However, on a smartphone, the benefits are far less significant than the company suggests.
Two mini use cases
That being said, the feature does have two minor uses. Firstly, the variable aperture allows you to deliberately increase exposure time to create motion blur. Though, only within a narrow range of ambient light. The iPhone’s aperture can be adjusted from just ƒ/1.48 to ƒ/4. Outdoors, in daylight, the shutter speed is still much too fast, even at ƒ/4. And in very low light, it doesn’t make any difference, because you’ll be opening the aperture all the way anyway. At best, it’ll make a difference in a handful of scenarios – and only at dusk.
The second benefit of the variable aperture is similarly limited. Videos look more natural when the shutter speed of individual frames is about half the frame rate. For example, 1/60 second at a frame rate of 30 frames per second (FPS). This is because our eyes expect some motion blur in videos. Again, in specific lighting situations, the variable aperture can be the deciding factor in whether to set the shutter speed to 1/250 or 1/60 of a second. In most cases, though, you’ll still need an ND filter if you want to pull this off.
The hidden reason
So why has Apple introduced a variable aperture? Probably because the feature increases light intake without the disadvantages outweighing the advantages.
The main camera on the previous iPhone has a lens with a fixed aperture of ƒ/1.78. On the new iPhone 18 Pro, the widest setting is ƒ/1.48 – a difference of about half a stop. In other words, the lens can capture about 50 per cent more light when the aperture is fully open.
Letting in more light gives you the edge in the evening or in dimly lit indoor spaces. In those scenarios, the camera has to boost sensor sensitivity (ISO) so that the shutter speed is fast enough and the photo remains in focus. This causes image noise, reducing image quality. Alternatively, your phone will switch to night mode, forcing you to hold the camera steady for a long period. At ƒ/1.48, the camera doesn’t have to increase the ISO as much as it does at ƒ/1.78. In other words, you don’t need to keep the iPhone still for as long. However, the real-life difference is negligible.
The problem with higher light intensity is that it causes more reflections inside the lens. This makes images less sharp, especially at the edges. In lenses used in large-format cameras, this is corrected with complex lens designs. But there isn’t enough space for that in a smartphone.
In low light, this compromise is worth it. A lower ISO is more important than a sharper image. In good lighting conditions, however, the iPhone’s ƒ/1.48 lens would perform worse than its predecessor. The ISO is already set to the minimum in this scenario, so the only drawback is the reduced sharpness.
A variable aperture solves this very problem. In low light, the camera can open the aperture and doesn’t have to increase the ISO as much. In good lighting, it reduces the aperture, and the image is just as sharp as with the iPhone 17 Pro. It’s a win-win.
Verdict: a tiny bit better
As it turns out, the iPhone 18 Pro really does take better photos than its predecessor in some situations. It also opens up new opportunities in niche scenarios. The thing is, you’d need a magnifying glass to spot the differences. Not to mention the fact that the greater «control over exposure and depth of field» is largely a myth.
Is this Apple’s «biggest camera improvement in years»? In my view, absolutely not. Instead, the iPhone 18 Pro has followed a path already well trodden by its predecessors: the improvements, taken individually, are minor. So if you have an iPhone 17 Pro and were considering upgrading purely because of the variable aperture, don’t bother. Even for photography enthusiasts, the feature isn’t worth it. It takes several generations for camera upgrades to add up to noticeably better images.
I’ll be publishing a detailed review of the iPhone 18 Pro (focusing on aspects other than the new variable aperture) in the coming weeks. Don’t want to miss it? Feel free to follow me below.
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