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OIS - Optical Image Stabilization - Gary explains!
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.
“Camera shake is the thief of sharpness.”
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 microcontroller 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.
It is important to note that image stabilization does not prevent motion blur caused a moving subject.
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 microcontroller 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 microcontrollers for OIS often come from ARM, this time not the Cortex-A range of CPUs, but the Cortex-M range of microcontrollers.
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.
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Note 5 vs Nexus 6P
To show you OIS in action I have put two smartphone cameras to the test. The first is the Samsung Galaxy Note 5, which has OIS, and the second is the Nexus 6P, which doesn’t have OIS. Trying to find a method which produced consistent (and reliable) results is quite hard. I tried several different ways of taking photos, while shaking the camera, however I couldn’t find any consistency until I tried jumping! So to test these two cameras what I did was jump in the air and then take a photo while I was in the air, but still moving. I did this several times to make sure I was doing it right!
So here are two galleries of pictures taken with the Nexus 6P and the Note 5. Before you take a looking let me point out that a) I took the pictures indoors intentionally so that there is less light available thus forcing a longer exposure time, b) there will be other factors that alter the resulting images including the overall speed of the image sensor etc.
So first the Nexus 6P:
And now for the Note 5:
Take a look at the two galleries and form an overall impression of the results. What do you think? For me I see that both phones took blurred pictures and both phones took clearer pictures. So obviously things like the sensor speed and my erratic jumping play a part. However I also see that the Note 5, with its OIS system, took less pictures that were blurred when compared to the Nexus 6P.
What do you think?
How important is OIS to you? Are features like 4 axis OIS, that was announced for the Xiaomi Mi 5, important to you? When you buy a phone do you see OIS as a must have feature? Please let me know in the comments below.