How blurry or clear a photograph will be depends on the aperture of the lens. The aperture of the lens controls the amount of light that enters the lens and falls on the image sensor through a mirror. This is because the aperture of a lens is basically the opening. The lesser the opening, the lesser the light enters and hence the resulting image would be darker and blurry.
Similarly, the greater the opening, the brighter the picture will become and it can be blurry again if the aperture is too wide. The aperture settings are a vital part of photography of any kind.