The phrase describes a situation where a mechanical incompatibility arises when attempting to connect a Nikon AI-S (Aperture Indexing Shutter) mount lens to a Canon EF (Electro-Focus) mount camera body using an adapter. This typically manifests as the adapter failing to properly attach to either the lens or the camera, or both, preventing the intended combination of legacy lens and modern camera from functioning. An instance of this would be purchasing an adapter intended to allow the use of a classic Nikon manual focus lens on a Canon EOS digital camera, only to find that the adapter locks neither securely onto the lens nor correctly into the camera’s lens mount.
The proper fit of lens adapters is critical to their functionality. A secure connection ensures correct flange distance, which in turn guarantees accurate focus. Failure to achieve this fit negates the primary benefit of the adapter: to expand the usable lens selection on a given camera body, allowing photographers to leverage the unique characteristics of vintage lenses, often at a more affordable price point than modern equivalents. Historically, lens adapters have provided an economical route for photographers to access different optical qualities without purchasing entirely new lens systems; therefore, incompatibility issues can frustrate this cost-effective strategy.
