This T2 mount adapter allows T-2 (42mm x 0.75) mount lens to fit onto your Canon EOS R RF mount mirrorless full frame camera bodies. This adapter will not affect your lens aperture control.
You can therefore shoot with manual mode or aperture priority mode.
The "Release shutter without lens" mode (C.Fn5) should be switched on before using this T2 Mount adapter.
The adapter is designed to allow your lens to focus on infinity.