Canon EOS R5 User Guide,  Tutorials

Using Adapted Lenses on the Canon EOS R5

August 1, 2025 /

When mounting a ‘mechanical’ adapter, that is one that has no electronic connection, the camera does not recognise that an adapter is attached, even if a lens is mounted on it.

The Canon EOS R5 is delivered from the factory with the option to operate mechanically adapted lenses disabled (as are other EOS R cameras). No doubt this is to protect the shutter blades and sensor, but it means you will have to enable the option, which Canon describes as ‘release shutter without a lens attached’. This presumably refers to operating the camera to check the shutter operation, but more often than not, I suspect users are going to want to enable this to use an adapted lens other than a Canon EF model. The option can be left enabled when using native RF mount and EF-adapted lenses.

How to release the shutter with a mechanical adapter and lens attached

  1. Turn on the Camera: Power on your Canon EOS R.
  2. Access the Menu: Press the Menu button on the back of the camera.
  3. Navigate to the Custom Functions:
    • Use the camera controls, such as the multi-controller (joystick) or touchscreen, to navigate to the Custom Functions section (represented by the wrench icon).
  4. Select C.Fn Settings:
    • Look for the C.Fn settings, which are labelled as Custom Functions 4 (C.Fn4).
  5. Locate the option, Release shutter w/o lens.
  6. Enable the Setting:
    • Change the setting to On (enable). This allows the camera to take a photo even when no lens is attached.
  7. Exit the Menu: Press the Menu button again to exit.