In a pinhole camera, a very small pinhole produces a sharp image because light rays from each point on the object pass through a single tiny opening and hit the screen in a small, focused area. When the pinhole is made larger, rays from the same object point can travel through different parts of the hole and spread out over a wider area on the screen. This results in blurred spots (larger circles of confusion) instead of sharp points, making the image less sharply defined. Although a larger pinhole allows more light and makes the image brighter, it sacrifices sharpness.