Variable aperture is not limited to professional cameras anymore. In smartphone cameras, this technology has evolved from an early experiment into an increasingly sophisticated hardware feature, particularly with the rise of larger image sensors.
Smartphones with a fixed aperture generally use a very wide aperture to maximize light capture across a broad range of shooting conditions. By contrast, a variable aperture allows the physical opening of the lens to be adjusted, giving the camera an additional degree of control over the amount of light reaching the sensor and, to some extent, depth of field. But how much does this additional flexibility translate into a real image-quality advantage?
Today, variable aperture is featured in a growing number of flagship devices and plays a role in achieving high image quality across a wide range of shooting conditions.
Based on our testing of smartphones equipped with variable aperture, we take a closer look at where this technology can make a measurable difference and why the way it is integrated into the overall imaging pipeline matters just as much as the hardware itself.
Variable Aperture: Where does it make a difference?
We previously explored how variable aperture works in smartphone cameras in our article https://www.dxomark.com/understanding-variable-aperture-in-smartphone-cameras/
This time, we are looking at the technology from an image quality perspective, based on our testing of devices equipped with this type of optical system.
Greater depth of field for group portraits
One of the most visible benefits of variable aperture is its ability to control depth of field.
By stopping down the aperture, the camera can increase the depth of field and keep a larger portion of the scene in focus. This can be particularly useful for group portraits and
This is especially relevant for smartphones equipped with large sensors, where the combination of a large sensor and a wide aperture can naturally produce a shallow depth of field.
Our testing shows how this can translate into a practical advantage. When several subjects are positioned at different distances from the camera, using a narrower aperture can increase the probability that all of them remain sharp, reducing the risk of some faces falling outside the focus plane. A narrower aperture can increase the depth of field and help keep multiple subjects in focus.
Huawei Mate 50 Pro – wide depth of field keeps all subjects in focus
Software sharpening can sometimes compensate for insufficient detail in out-of-focus areas, but this does not recreate the information captured when the subject is actually within the optical depth of field.
vivo x300 Ultra – equiped with fixed aperture (f/1.9)
Background subject slightly out of focus
Huawei Pura 80 Ultra – equipped with variable aperture (f/1.6 – f/4)
Consistent sharpness on face in group portraits
Greater tolerance to autofocus errors
Variable aperture can also influence autofocus performance.
Stopping down the aperture increases depth of field, making the image less sensitive to small focusing errors. In practical terms, this can increase the tolerance of the camera system when subjects are positioned at different distances or when the autofocus system does not lock precisely on the intended subject.
This is particularly relevant for challenging scenes such as group portraits or close-up photography.
The Huawei Pura 80 Ultra provides an interesting example. The combination of its optical system and camera processing contributes to strong autofocus performance, with the device achieving one of the highest DXOMARK scores for autofocus sharpness and timing.
Autofocus tests concentrate on focus accuracy, focus repeatability, shooting time delay, and depth of field. Shooting delay is the difference between the time the user presses the capture button and the time the image is actually taken. It includes focusing speed and the capability of the device to capture images at the right time, what is called ‘zero shutter lag’ capability. Even if a shallow depth of field can be pleasant for a single subject portrait or close-up shot, it can also be a problem in some specific conditions such as group portraits; Both situations are tested. Focus accuracy is also evaluated in all the real-life images taken, from infinity to close-up objects and in low light to outdoor conditions.
The benefit of variable aperture here is therefore not simply about producing a sharper image. By increasing depth of field when appropriate, the camera can make focus errors less visible and improve the consistency of the captured image.
Improved Sharpness and Exposure Control in Low Light Conditions
Variable aperture also gives manufacturers greater flexibility in managing the trade-off between light capture and optical performance.
A wider aperture allows more light to reach the sensor, which is particularly valuable in low-light conditions. A narrower aperture reduces the amount of incoming light but can increase depth of field and, depending on the optical design, help control certain aberrations and improve image uniformity.
Our testing highlights the importance of this trade-off.
In low-light scenes, opening the aperture can help the camera maximize the available light and preserve detail while limiting noise. In brighter scenes, stopping down can provide greater depth of field without necessarily compromising exposure.
The ability to adapt the aperture therefore gives the imaging pipeline another parameter to work with.
Rather than operating the camera at a single fixed aperture in every situation, the system can select an aperture according to the scene, balancing exposure, depth of field, optical performance, and other image-quality considerations.
Managing flicker in video
Variable aperture can also have an interesting role in video, particularly under artificial lighting.
Many LED light sources exhibit temporal variations caused by pulse-width modulation (PWM) or mains-frequency cycling. Depending on the exposure time, frame rate and rolling-shutter behavior of the camera, these variations can result in visible flicker or banding.
Stopping down the aperture reduces the amount of light reaching the sensor, potentially allowing the camera to use a longer exposure time. This can help average variations in the light source over a greater portion of the capture period and reduce visible flicker.
Hardware alone does not guarantee better image quality
The presence of a variable aperture does not automatically translate into better image quality.
Its effectiveness depends on how the hardware is controlled and integrated into the camera’s broader imaging pipeline.
The system needs to determine when to open or close the aperture and how this decision interacts with auto-exposure, autofocus, HDR processing, image fusion and other computational photography algorithms. This is particularly important because the optimal aperture can vary significantly depending on the scene. A setting that is beneficial for a group portrait may not be appropriate for a low-light scene, while the requirements for photography can differ from those for video. The behavior of the complete camera system needs to be assessed across a range of real-world conditions.
The Xiaomi 13 Ultra, for example, illustrates the importance of this interaction. Its variable-aperture system provides additional optical flexibility, but the resulting image quality ultimately depends on how effectively the camera combines aperture selection with exposure and autofocus strategies.
Xiaomi 13 Ultra – f/4.0
Background subject slightly out of focus
Background subject in focus
What are the limitations?
Variable aperture brings clear benefits, but it also introduces additional complexity.
Compared with a fixed-aperture design, the mechanism requires additional components and space within the camera module. It can also increase manufacturing complexity and potentially introduce additional considerations around reliability and mechanical precision.
These constraints help explain why the technology remains primarily associated with high-end smartphones.
At the same time, the increasing use of large sensors and sophisticated optical systems could make variable aperture an increasingly relevant tool for manufacturers looking to extract more performance from smartphone camera hardware.
Variable aperture: another degree of freedom for smartphone cameras
Our testing shows that variable aperture is not simply about controlling how much light reaches the sensor.
Its most meaningful benefits come from giving the imaging system an additional degree of freedom to adapt to different shooting conditions. In group portraits, this can help increase depth of field and maintain sharpness across multiple subjects. In autofocus, it can provide greater tolerance to small focus errors. In low light, opening the aperture can maximize available light, while in video, aperture control can contribute to better management of challenging artificial lighting.
At the same time, these benefits depend heavily on implementation. Aperture selection needs to work in conjunction with exposure, autofocus, sensor characteristics, optics and computational processing.
As smartphone camera architectures continue to evolve, we will continue to investigate how new optical and computational technologies translate into real-world image quality.
