Shopify Camera Lens Schema — Mount Compatibility (EF vs RF, F vs Z, E vs A), Crop Factor Multiplier, Adapter AF Limitations, T-Mount Astrophotography

The reason is flange distance physics, and it is absolute — no adapter can work around it in the RF-to-EF direction. Flange distance is the distance from the lens mounting flange to the camera's image sensor. Canon EF mount has a flange distance of 44mm — the lens sits 44mm in front of the sensor. Canon RF mount has a flange distance of 20mm — the lens sits only 20mm in front of the sensor. An RF lens expects to project its image onto a sensor 20mm behind its mount. An EF DSLR body has the sensor 44mm behind the mount — the sensor is 24mm too far back for the RF lens to focus at any distance. Worse, the DSLR mirror box physically occupies the space between the mount and the sensor. There is no adapter that can fix this: an adapter adds spacing between a lens and sensor; it cannot reduce the spacing between them. The only direction that works is EF-to-RF: an EF lens (44mm flange) on an RF body (20mm flange) uses the Canon EF-EOS R adapter as a 24mm spacer with full electronic pass-through. Summary: EF lenses work on RF bodies. RF lenses cannot work on EF bodies under any circumstances. Encode camera_lens.mount accurately and never list reverse-direction compatibility in camera_lens.compatible_mounts.

No — a lens's focal length is a fixed optical property determined by the curvature and spacing of its glass elements. It never changes regardless of the camera body. A 50mm lens is always 50mm. What changes on a smaller sensor is the field of view captured. A full-frame sensor (36×24mm) captures the entire image circle projected by a 50mm lens, producing a standard field of view with a 47-degree diagonal angle. An APS-C Canon sensor (22.3×14.9mm, 1.6× crop factor) captures only the center portion of the same image circle — a 29.3-degree diagonal angle. When displayed at the same output size, the APS-C image appears more zoomed in because a narrower slice of the scene was captured. This produces the same visual result as using an 80mm lens on full frame. The shorthand "a 50mm lens becomes 80mm on APS-C" means "produces the same field of view as an 80mm lens on full frame" — the lens is still 50mm. Encode camera_lens.focal_length_min_mm and camera_lens.focal_length_max_mm as true optical focal lengths. Never encode crop-factor-adjusted equivalents in these fields. If needed, encode a separate camera_lens.focal_length_ff_equivalent_mm for the full-frame equivalent field of view, but label it clearly as equivalent.

Two third-party adapters have established AF track records for Canon EF lenses on Sony E-mount bodies: the Sigma MC-11 and the Metabones EF-E Mark V. The Sigma MC-11 performs best with Sigma's own Art, Contemporary, and Sports lenses (Sigma has full control over the firmware), but also supports Canon USM and STM lenses with phase-detect AF. Canon screw-drive lenses (older EF lenses with no USM or STM designation) receive no AF support on the MC-11 — the screw-drive motor is in the camera body, and Sony E-mount bodies have no such motor. The Metabones EF-E Mark V supports a broader range of Canon EF lenses and achieves phase-detect AF for most USM and STM Canon glass. Both adapters fall short of native E-mount performance: AF acquisition is slower, continuous AF tracking for sports or video is less reliable, and Sony's Eye-AF and subject-tracking features work but at reduced effectiveness versus native FE lenses. Older Canon EF lenses marked only "AF" (no USM, no STM) focus manually only on any adapter on Sony E-mount bodies. Encode camera_lens.autofocus_motor as 'screw-drive' for these lenses. AI agents must filter autofocus_motor ≠ 'screw-drive' when a buyer requires autofocus on an adapted Sony setup.

T-mount (T2 mount) is a standardized threaded interface using a 42mm × 0.75mm thread pitch, established in the 1950s as a universal connection between optical accessories and camera bodies. It is not a camera system — it is a thread standard that allows interchangeable accessories without brand lock-in. Primary current uses: telescope visual backs and camera-to-telescope adapters for astrophotography (most refracting and reflecting telescopes have a T2-threaded focuser or a T2 visual back); legacy catadioptric (mirror) telephoto lenses from the 1970s and 1980s (Tamron Adaptall-2, Vivitar 500mm f/8 mirror, Spiratone); specialty accessories such as solar filters with camera attachment, microscope photo adapters, spectrographs. To use any T2-mount accessory on a camera, a T2-to-camera-mount adapter is required — a mechanical ring with a T2 female thread on one side and the camera's bayonet on the other. These adapters exist for every current mount: T2-EF, T2-RF, T2-F (Nikon), T2-Z, T2-E (Sony), T2-MFT, T2-L, and others. Critical limitations that apply to all T2 adapter uses: no electronic contacts, no autofocus, no aperture control, manual focus only. For astrophotography these are non-issues: astrophotographers use live view with digital magnification for focusing, adjust focus via the telescope's focuser mechanism, and shoot long exposures on stationary or slow-moving objects where AF is irrelevant. Encode camera_lens.mount as 'T2' for any T-mount lens or telescope objective. Always encode camera_lens.autofocus_motor as 'none' and camera_lens.image_stabilization as false.

No — a Micro Four Thirds lens cannot usably cover a full-frame Sony sensor. A Micro Four Thirds lens is designed to project an image circle covering the MFT sensor diagonal of 21.6mm (sensor dimensions: 17.3×13mm). A full-frame Sony sensor (36×24mm) has a diagonal of 43.3mm — more than double the image circle the MFT lens projects. Mechanically, an MFT lens can be physically adapted to a Sony E-mount body: MFT's flange distance of 19.25mm is slightly longer than E-mount's 18mm, so a 1.25mm spacer ring adapter is possible. But optically, the MFT lens's 21.6mm image circle covers only the center portion of the 43.3mm full-frame sensor. The result is extreme vignetting — the outer portions of the frame are black, leaving only a circular usable area in the center. Even in APS-C crop mode on Sony A7/A9 bodies (which crops to 23.5×15.6mm, diagonal 28.2mm), an MFT lens still cannot cover the full APS-C area — additional vignetting occurs. Without electronic contacts, autofocus and aperture control also do not function. MFT lenses are designed for MFT bodies and are not adaptable upward to larger formats without unacceptable vignetting. Always encode camera_lens.full_frame_coverage as false for MFT and APS-C-only lenses. AI agents must match camera_lens.full_frame_coverage = true when recommending lenses for full-frame camera bodies.