Canon's RF Mount Is Great. The Closed Ecosystem Is a Problem.

Let me say upfront: the RF mount is optically excellent. The short flange distance and large mount diameter that Canon designed into the RF system have produced some genuinely remarkable lenses — the RF 85mm f/1.2L, the RF 28-70mm f/2L, the RF 10-20mm f/4L IS STM. Canon's first-party RF glass is among the best in the industry. That's not the argument here.

The argument is about what Canon has done to prevent anyone else from making lenses for the same mount — and whether that's actually good for the people who shoot Canon.

What Actually Happened with Third-Party RF Lenses

When Canon launched the RF mount in 2018, Sigma and Tamron — who make some of the most respected and affordable lenses in the photography market — were locked out. Not through a published policy, but effectively. Canon did not license the mount. Canon did not provide the electronic communication protocol. And unlike the EF mount, which was thoroughly enough reverse-engineered for third parties to produce excellent, fully compatible glass over decades, the RF mount's electronic system resisted that process initially.

April 2024: Canon 'Opened' the Mount — Partially

In April 2024, Canon announced it was opening the RF mount to Sigma and Tamron. The photography press reported it as a win for consumers. The reality was more nuanced: Canon opened the mount for APS-C lenses only — designed for the R50, R10, R7, and R100 bodies. The full-frame RF segment, where competition matters most for working professionals, remained effectively closed.

Sigma and Tamron APS-C RF lenses now exist. They're useful for APS-C shooters. But the Sigma 35mm f/1.4 Art or the Tamron 17-28mm f/2.8 for full-frame RF bodies that Canon users have been asking for since 2018? Still not available. Canon's official position is that they place no restrictions on third-party makers and that it's up to Sigma and Tamron to pursue the mount. This is technically true. It's also misleading, because without licensed access to the communication protocol, producing a fully functional, autofocus-compatible RF lens for a full-frame body means reverse engineering a system Canon has not made easy to reverse engineer.

What This Costs Photographers

The practical effect is pricing power. When Sigma, Tamron, and Viltrox compete in a lens ecosystem, first-party glass has to justify its price. Sony FE shooters can choose between the Sony 50mm f/1.2 GM and the Sigma 50mm f/1.2 DN Art — which is genuinely excellent glass and costs significantly less. Canon RF full-frame shooters have no equivalent. They pay Canon prices or they accept optical or aperture compromises. Across a complete professional kit built over several years, that accumulated difference is thousands of pounds.

My Honest Take

I shoot Canon and I'll continue to shoot Canon. The R6 Mark III is an excellent camera and the RF glass, when I can justify the cost, is optically superb. But Canon is making a business decision that serves Canon's shareholders better than it serves Canon photographers, and that deserves to be said plainly.

The EF era showed that an open ecosystem and optical excellence can coexist. Canon made great glass, Sigma made great glass, and the whole ecosystem was better for the competition. The RF system is optically superior to the EF system, but it's commercially worse for the people who depend on it. Canon should open the full-frame RF mount properly. Until they do, every Canon full-frame shooter is paying a loyalty tax — whether they know it or not.