In early 2019, Rodenstock developed and manufactured a new shutterless lens mount called the Aperture-Only (AO) mount, or the Aperture-Stop mount. Deliveries of lenses with the AO mount began in late 2019.

Dimensions of the new AO mount are identical to a Copal 0 shutter, and have the same spec for thread mounting. The AO mount can be a direct replacement for a Copal 0 shutter when needed.

Sturdy lens mount construction

The AO lenses feature a sturdy mount construction and a nine-blade aperture design that creates an almost perfect circular aperture opening. The AO mount is purely mechanical in operation, eliminating the need for battery power, additional controllers, or cables.

When focusing, rotate the aperture control ring to the AO lens widest opening. Once focused, select an aperture for shooting by rotating the aperture control ring until the desired f/stop lines up with the white index mark on the mount.

Rodenstock's Aperture Only (AO) lenses are designed exclusively for cameras with focal plane shutters or digital backs with electronic internal shutters. Specifically, AO lenses are suitable for digital backs such as the Phase One IQ4 series or Hasselblad H6D & 907X, or for digital cameras used as the capture device on a view camera - Canon R, Fuji X & GFX, Hasselblad X1D & X2D, Leica S, Nikon Z, and Sony mirrorless cameras.

Rodenstock AO lenses do not provide a sync terminal for strobe lighting. Therefore, exposure control and strobe syncing must be managed by the capture device - either a digital back or a digital camera.

It's important to bear in mind that using the electronic shutter of a digital back or mirrorless camera may have limitations when photographing fast-moving activity such as vehicles or people. This is due to the possibility of a distorted effect, called rolling shutter, when fast-moving subjects pass closely to the camera position during exposure. However, rolling shutter typically causes little to no problem for photographers capturing static landscape and architecture, or studio subjects.