I love my Voigtländer lenses for the Nikon Z. They are compact, sharp, and the focus ring is a dream to use. But one thing has always bothered me: the aperture ring is very smooth and therefore very easy to adjust unintentionally. Especially since it is located at the front of the lens and not only the ribbed area but also the tube behind it are part of the aperture ring, it often happens that your fingers slip beyond the focus ring onto the aperture ring when focusing, thus unintentionally adjusting the aperture value. My solution for this is to screw on a step-up ring and insert a suitable rubber ring into the gap between the aperture ring and the step-up ring. This increases the friction of the aperture ring slightly, making it harder to adjust. The main problem, however, is finding suitable BLACK rubber rings; they are often too thin, so you have to use two or three on top of each other.
