How is aperture adjusted with this adapter since G-lenses for Nikon, for example, do not have aperture rings?
I'm afraid I don't understand your question. This unit is not for Nikon F mount lenses. This unit is a Contax G Lens to Fuji X Adapter. Contax G is not related to Nikon F. With Nikon G series indicates F mount (AF-D or AF-S type) lenses without an aperture ring, it is not technically a mount in and of itself.