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Canon Patent Application: Triple-IS Image Stablization
Buried deep in this patent application is an embodiment of something that I could certainly see Canon implementing over time after they get in body image stabilization (IBIS) working well. This is triple-IS. Dual IS is using the lens image stabilization and the camera image sensor stabilization together to optimize the stabilization, Canon also calls this Dual IS when it's the optical lens IS and electronic IS working together as well. Essentially, two different image stabilization schemes working together.
This method of image stabilization is for video only.
Canon is considering, in this patent application Triple-IS.
- Lens based Image Stablization
- Image Sensor Image Stablization
- Electronic Image Stablization
What the patent application mentions are;
The following embodiment describes a mode in which the present invention is implemented as an image capturing system that includes a camera body and an interchangeable lens. Note that the image capturing system according to the present embodiment further includes the function of performing shake correction by controlling the position and the rotation of the image sensor, in addition to optical shake correction by driving the shift lens and electronic shake correction performed by controlling a region that is to be extracted from a captured image, which are described above.
and further on;
On the other hand, in the camera body 620 according to the present embodiment, the image capturing unit 109 includes an image sensor configured to be rotatable about the optical axis and movable in a direction that is orthogonal to the optical axis, a driving mechanism for driving the image sensor, a state detection sensor, and so on. The driving of the image sensor is controlled by an image capturing shake correction control unit 622. That is, in the image capturing system 600 according to the present embodiment, the image sensor and the image capturing shake correction control unit 622 are components for correcting an image blur caused by shake of the image capturing system 600. The image capturing shake correction control unit 622 corrects an image blur by driving the image sensor so as to correct displacement and rotation of an optical image of the subject formed on the image sensor, caused by shake. Thus, in the present embodiment, the image sensor and the image capturing shake correction control unit 622 serve as a third correction means according to the present invention, which realizes a mechanical shake correction type correction function, by which an image blur is mechanically corrected.
So what's the goal of all this?
There are two types of shake. Low frequency is when you are hand holding and there's a slight movement in a general direction, more like drifting. High frequency is when things are jittery and there are lots of small, but frequent movements. Like when I drink too much coffee.
Optical and Image sensor stabilization works great with high-frequency shake, electronic stabilization works best with low-frequency shake. The camera monitors the shake and determines which system should correct the shake being detected.
According to Canon, what can happen in low light situations and slow shutter speeds is something they call accumulated shake. Accumulated shake is what happens when the image sensor is actively capturing an image, motion blur during this time cannot be corrected by electronic image stabilization because the motion blur has already happened during the image sensor accumulation because the shutter speed is slow. Thus the term "accumulated shake".
Accumulated shake is most likely low frequency because that shake is handled by electronic image stabilization. Thus the problem. For slow shutter speeds, you can't rely on Electronic image stabilization to correct for low-frequency shake as much as you can with a fast shutter speed.
What Canon is stating (I believe) in this patent application is that they are changing it so that optical and sensor image stabilization is used for more low-frequency shake as the exposure time increases, and that how the vary image stabilization pieces interreact is determined by the shutter speed.
This leads to better image stabilization when using slow shutter speeds to shoot video.
US Patent Application 20190199930
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