The brand new Nokia Lumia 928 comes with the most innovative and advanced smartphone camera package available today, producing great pictures both day and night. Keen to know more, we asked Nokia’s head of imaging technologies, Juha Alakarhu, about the magic mix of components and software that makes the PureView camera in the Lumia 928 (and Nokia Lumia 920 before it) work so well.
Large 8.7-megapixel sensor
The most important thing is the image quality. Every time we are developing a new camera module, we carry out an extensive technology evaluation and a lot of simulations for example on sharpness, and low light performance, and their subjective importance in different use cases. This process includes deciding the resolution of the camera module.
So why is Nokia’s camera sensor 8.7-megapixels?
It may seem like a strange number to pick, but it’s based on the fact that the sensor is specially designed so it can be ‘sliced’ in different ways to produce excellent results in either 4:3 or 16:9 modes. Juha notes that other smartphones are optimised just for one aspect ratio, 4:3 or 16:9, and the other is created by cropping from it. Nokia’s leading cameras take the full field of view in both aspects.
“You want a large aperture on a smartphone camera. It means the camera lets in more light. And that means better pictures with shorter exposure times, or when lighting is low,” explains Juha. Our solution for the Lumia 928 and 920 is an f2.0 opening, which is one of the largest in the industry. [NB: smaller numbers mean a bigger opening when it comes to camera apertures].
But making a large aperture poses its own design problems, so there are practical limits. “Fortunately, our partnership with Carl Zeiss has made it possible to have leading-edge optics that are entirely customised to our cameras.”
Optical image stabilisation
“We’re really proud of this,” says Juha. “It simply lets people take better pictures, without having to worry about the technology.” The lenses on the Lumia 928 (like the Lumia 920) are actually separately encased in their own unit and can move in X or Y directions to compensate for shaky hands, movement or longer exposure times.
While these adjustments happen, the lens always stays parallel to the sensor, which enables broader movement than, for example, solutions that tilt the lens. This way we can enable longer exposure time than anyone else without having handshake in the images. There is a whole white paper devoted to this technology, here.
“When you add our exclusive Carl Zeiss optics to this, it’s something unique and special.”
With the sort of mix we’ve described above, the physical components of the camera can provide a great basis for good pictures. But Juha stresses the importance of imaging algorithms in creating the best images. Nokia’s own proprietary technology decides how to best expose different parts of the image, how the colours are balanced, how best to eliminate noise, and dozens of other parameters. Finding the perfect balance for everything is like creating art!
“And the great thing about these software solutions is that they are portable to lower-cost phones and also upgradeable – we spend a lot of time reading feedback on our cameras from users and professionals to ensure we are fine-tuning them to deliver the best possible results based on people’s needs and experiences” says Juha. “As a result of this, you can guarantee that the camera on your Nokia Lumia will continue to improve through updates and new experiences. I would also say that, right from the start, we have the best smartphone camera technology at each price point.”
Superior flash solutions
On high-end Nokia smartphones, because of OIS, larger apertures, great image sensor technology and superior processing software, you can often take images without flash.
But there are still occasions when you need it: if you’ve got low light and movement to contend with, for example. In these extremes, the Lumia 928 has got your back with a powerful xenon flash that can freeze the scene to help you capture that moment with detail. It also gives you one more tool that you can you can use for your creative purposes. For example, try having both motion blur and “xenon freeze” in the same photo!
Sum of its parts
“You can have a great sensor, lenses, algorithms and mechanics. But if you haven’t got them all working in harmony together, you’ll end up disappointed. It’s all about balance between the ingredients, something we have really striven for with the new Nokia Lumia 928, as well its predecessors.” Juha concludes.