Monday, April 11, 2016

OIS: What is it and why is it important to have in your smartphone camera?

After a weekend volunteering at my daughter's gymnastics meet, I noticed quite a few parents pulling out smartphones to take pictures or video of their precious little one doing a beam or bar routine in front of a crowd for the first time. Of course I have seen it before, 9/10 parents at sporting events use a smartphone instead of a dedicated camera. The think I noticed was how much they moved the phone even when their kid wasn't really moving anywhere. Then when I noticed the type of phones they were using, they were ones with no OIS so my next thought was, that is going to be a blurry picture or shaky video. So, how does OIS help in picture/video taking and why should you consider getting a smartphone with it, especially if you have an active little one.

Optical Image Stabilization (OIS) is a feature that you find on the cameras of many high-end smartphones, but what exactly is it? And how does it work? Let’s find out.

Thinking in terms of a traditional camera, the process of taking a photo is like this: you set up your shot, you adjust the focus, aperture, and shutter speed and then you click the button to open the shutter and allow the light in so it can be captured on film or an image sensor. But here is the thing, if you move the camera, even a little, during the moment when you open the shutter and let the light in then the resulting picture will be blurred. In most cases, a blurred picture is a bad picture. As Canon puts it, “Camera shake is the thief of sharpness.” So, OIS is a technology that reduces the blurring caused by the motion of a camera during exposure.

Obviously if the shutter speed is high, meaning it opens and closes very quickly, then the amount of time when the camera needs to be steady is reduced. However if the shutter speed is low, for example in poor lighting conditions, then the amount of time the shutter stays open is longer and the amount of blurring due to movement/shake increases.

What OIS does is compensate for small movements of the camera during exposure. In general terms this is achieved by the use of a floating lens, gyroscopes and small motors. The elements are controlled by a micro-controller which moves the lens very slightly to counteract the shaking of the camera or phone, i.e. if the phones of is being moved to the right, then the lens is moved left. All very clever stuff, however, it is important to note that image stabilization does not prevent motion blur caused by a moving subject (e.g. a car, child, animal etc). Image stabilization is only able to reduce blur due to the small shaking of a lens when held in the hand. Cameras or phones placed in a tripod don’t need to use OIS.

Your basic OIS system uses two gyros in the lens (one for yaw and one for pitch) that detect both the angle and speed of the movement. This data is fed, in real-time, to the micro-controller which then moves things around inside the lens to compensate for the movement. Interestingly, the majority of smartphones use SoCs (System-on-a-Chip) based on the the ARM architecture and often use CPU cores and GPU designs made by ARM. Likewise the design for the micro-controllers for OIS often come from ARM, this time not the Cortex-A range of CPUs, but the Cortex-M range of micro-controllers.

Besides Optical Image Stabilization there are other Image Stabilization (IS) techniques which aren’t optical. For example during MWC 2016 OPPO announced that it has moved image stabilization out of the lens and into the image sensor. Oppo’s solution, known as SmartSensor, monitors the vibrations on the pitch axis, yaw axis and roll axis, and then compensates for them using a voltage-driven MEMS (microelectromechanical system).

Another type of IS is Digital Image Stabilization, where the image is shifted digitally in the from frame to frame, enough to counteract the motion. This technique is used mainly while recording video and is performed in software and does not rely on any mechanical components. Some smartphones have both OIS and DIS (sometimes called Video DIS) systems, the first for video and the second for recording video.

So the next time you upgrade to a new smartphone and you want a great camera for those one of a kind moments, ask if your choice has OIS. It will definitely make a difference and save you from a lot of those moments where you are deleting what would have been a memorable shot.

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