I asked Google Gemini and got the following information:
If you are finding that the
Canon RF 24mm f/1.8 Macro IS STM physically will not mount to your
Meike RF extension tubes, you aren't alone—this is a known issue caused by a physical mismatch in the mount design of this specific lens.
While the lens and the tubes both use the "RF mount," there are two specific reasons for this physical incompatibility:
1. The Protruding Rear Element "Skirt"
The RF 24mm f/1.8 Macro has a unique rear design. Unlike many other RF lenses (like the 50mm f/1.8), the 24mm has a
rectangular-ish plastic light baffle (shroud) that surrounds the rear glass element and the electronic pins.
- The Conflict: Many third-party extension tubes, including the Meike MK-RF-AF1, have an internal circular opening or a set of internal baffles that are slightly too narrow to accommodate this specific shroud.
- The Result: The lens hit a "hard stop" against the internal plastic of the extension tube before the bayonet lugs can fully seat and twist-lock into place.
2. Tight Manufacturing Tolerances
The Meike tubes are built with aluminum or plastic interiors that are designed to fit the
majority of RF lenses. However, the RF 24mm f/1.8 (and sometimes the RF 35mm f/1.8) has a slightly "chunkier" rear geometry because of its macro-optimized design and image stabilization assembly.
- Because Meike tubes are not "Official Canon" accessories (Canon does not currently make official RF-mount extension tubes), they weren't tested against the specific dimensions of the 24mm Macro during their initial engineering phase.
Which brands actually fit?
Since Canon does not make official RF extension tubes, you have to rely on third-party brands that have engineered a wider internal clearance. Based on user reports and technical specs:
- JJC (AET-CRFII): These are currently the most recommended alternative. JJC redesigned their RF tubes (the "II" series) specifically to have a wider internal throat to accommodate the "Macro" primes like your 24mm.
- Viltrox (DG-EOS R): Most versions of the Viltrox metal mount tubes fit the 24mm, as they use a more open internal design than Meike. However, some users find the fit a bit "loose" compared to JJC.
- Fotodiox: These are generally considered the high-end option for third-party tubes. They are built with tighter tolerances and almost always clear the rear baffles of the shorter RF primes.
