IS, or Image Stabilizer, is a camera or lens feature designed to reduce the effects of camera shake, helping produce sharper images in low-light conditions or when using long focal lengths. Originally developed for video cameras, the technology has been adapted for still photography, notably in Canon's EF lens series.
Understanding and using IS is essential for photographers who shoot handheld, in dim lighting, or with telephoto lenses. By compensating for small movements, the Image Stabilizer allows slower shutter speeds, reduces blur, and improves overall image clarity, making it a valuable tool for both amateur and professional photography.