Adjustment of the shading ring
The aperture of the lens can be divided into continuous aperture and discontinuous aperture. The continuous iris can be adjusted steplessly, and it can be adjusted at any position between the two stop iris. The discontinuous aperture can be adjusted according to the first, one-half, or one-third of the aperture, and there is a clear positioning feel when adjusting. Some brands of autofocus lenses do not have an aperture adjustment ring, and are adjusted by the camera's aperture adjustment mechanism, such as Canon's ef series lenses and Nikon's af g series lenses.
When adjusting the iris, the iris is always at the maximum aperture. Only when the shutter button is pressed to release the shutter, the aperture automatically shrinks to the set f-factor, and the aperture returns to the maximum aperture after the exposure is completed.