kontrastitunnistusta

Kontrastitunnistus, known in English as contrast detection, is an autofocusing technique used in digital cameras and other imaging devices. It relies on measuring the contrast of an image in different areas to determine the optimal focus point. The camera analyzes the image data, typically from the image sensor, and looks for areas where the brightness changes most sharply, indicating sharp edges and thus a well-focused subject.

The process involves taking multiple measurements of contrast within a designated focus area. The camera then systematically adjusts the lens position, moving it forward or backward, and measures the contrast at each position. The lens is moved until the contrast reaches its maximum value. This maximum contrast point is considered the point of sharpest focus. While generally effective and simpler to implement than phase-detection autofocus, contrast detection can sometimes be slower, especially in low-light conditions or when autofocusing on low-contrast subjects. It is commonly used in mirrorless cameras, smartphone cameras, and some camcorders.