Image stabilization
Image stabilization, also known as IS, is a technique to reduce unwanted photographic effects caused by the movement of a digital camera.
For a still image, IS attempts to eliminate the blur that results if the camera is moving when the image is captured. For a video, IS can adjust the position of consecutive video frames, to simulate a motionless camera.
IS can be performed by optical or digital hardware when the images are captured, or as a post-processing step performed by specialized software. It primarily compensates for pan (horizontal rotation), tilt (vertical rotation), and roll (axial rotation), and minor camera repositioning.
Optical Image Stabilization
Optical Image Stabilization, frequently abbreviated as OIS, refers to an image stabilization method built into the hardware of the camera. The OIS physically moves the camera lens to accommodate for any small accidental movements made while capturing a photo or video. The movements are detected by gyroscopes, and a small motor that makes a movement in the opposite direction, stabilizing the image.
Optical Image Stabilization is generally more effective than digital alternatives. For this reason, OIS is a feature found in most modern cameras and flagship smartphones. Third-party accessories like gimbals can also be used to stabilize footage without software.
Digital Image Stabilization
Digital Image Stabilization refers to methods of image stabilization performed through software. This feature is added to a camera or smartphone through a software update, not requiring any hardware installed on the device. Instead, a program analyzes footage and detects movements, moving the image on the X and Y axes to counteract the movement. Because of the adjustments, it has to make, Digital Image Stabilization generally crops the image, removing content from the edges of the frame.
Digital Image Stabilization is done automatically by the camera or smartphone application. Alternatively, editing programs like Adobe Premiere and Hitfilm have built-in image stabilization, allowing customization of the frame that's cropped out and the intensity of the corrections.
If you're planning on digitally stabilizing footage as you capture it, make sure to shoot wider footage than you need so you don't lose anything important when the edges are cropped.