critical aperture

Critical aperture is an important concept in photography and other optical systems. In basic terms, it's the size of a hole that lets light through a lens onto a camera's sensor or film. The size of the hole is important because it affects how much light can go through the lens and how much of that light is focused onto the camera's sensor or film. The bigger the hole (or the wider the aperture), the more light can go through. But, if the aperture is too wide, the light might not be focused accurately and you could end up with blurry or distorted images. If the aperture is too small, then the images may not be bright enough. The best size for a critical aperture is usually somewhere in between these two extremes.