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April 8, 2015

Lumia Imaging: Auto-focus and fixed-focus explained

With top-notch imaging technology, Microsoft’s Lumia smartphones are capable of capturing the world in breathtaking detail.

Some phones come equipped with auto-focus while others have fixed focus. But what’s the difference? Let’s explain, starting with the basics.

Every camera has a lens (or lenses) and a sensor and they’re responsible for different things. Light comes in through a camera’s lens and projects an image onto its sensor. It’s the lens that does the heavy lifting when it comes to focus.

Fixed focus


“[With fixed focus], you don’t need to worry about focusing, you just capture images instantaneously,” said Juha Alakarhu, director of imaging technology development at Microsoft.

“In autofocus, there is a short time that the camera needs to find the perfect focus.”

In fixed-focus cameras, the lens can’t be adjusted. Because of that, the focal point is set to so-called hyperfocal distance.

This position optimizes the depth of field so that everything from the nearest focus point (about 50 centimeters) to infinity is in focus. Consequently, these cameras are designed so that the depth of field (DOF) is as long as possible.

A common mistake that people make is to think that fixed-focus cameras are focused to infinity, but this is not the case.


Devices with fixed focus: Lumia 430 Dual SIM, Lumia 435, and Lumia 532.

Auto focus


“Auto focus enables maximum creativity because the focus position is optimized for each image separately,” said Juha.

Rather than a static, fixed lens, the lenses in an auto-focus camera can move closer or farther away from the sensor.

That way, whether you’re taking close-ups or scenery shots, you get the optimum sharpness. Auto-focus also makes it possible to zoom in for an extreme close-up of a subject, like when you take macro shots for example.

“In camera design, one of the first key questions is whether it is an auto-focus camera or fixed-focus camera. Auto-focus cameras have greater flexibility in overall design because you don’t need to worry about keeping the DOF as long as possible.

“We can use bigger sensors and a larger aperture in optics, which makes the DOF shallower and enable a beautiful bokeh effect in close ups.” Juha continued.

When you use an autofocus camera, Lumia camera focuses when you half-press the camera button or tap the area on the screen that you want in focus.

Lumia camera has also a special function for photography enthusiasts: Manually focus by using the slider in between white balance and ISO setting in the user interface.


Devices with auto focus: Lumia 640 XL, Lumia 830, and Lumia 930.

Whether you’ve got a Lumia with a fixed or auto-focus, Microsoft’s strong imaging innovations portfolio means you’ll always be able to take the best shot.

Share with us your best photo and let us know whether you use auto-focus or fixed focus.