SIGMA will announce two new Contemporary prime lenses soon

entoman

wildlife photography
May 8, 2015
325
332
UK
Sometime ago, I saw a post by a Canon Japan rep that stated competitive lens Mfgs are exactly that, competitors and to my knowledge, Canon has never shared their tech data with 3rd party lens Mfgs., which leaves reverse engineering their only alternative. . Competitors are not making knock offs or illegal copies. They're just trying to make EF and RF compatible lenses. I don't see the legal restrictions or patents being the problem here. If they were, you wouldn't see Samyang/Rokinon producing RF mount lenses, already. I feel sure that Canon hasn't shared any RF tech data with them.
Almost certainly, Samyang are just continuing to use the EF protocol (reverse-engineered) and have simply changed the dimensions of the mount.

There is of course no reason why Tamron, Sigma and others can’t do the same. My guess is that they are delaying release of such lenses for 3 reasons:
  • they want to design new lenses to take advantage of the shorter flange distance.
  • they can barely keep up with demand for their existing lenses.
  • Supply chain issues (chips etc)
I’m also guessing that Samyang/Rokinon, in common with Venus Optics, are at the moment primarily targeting the low demand niche markets, i.e. they are trying to plug the gaps not covered by other brands, hence RF.
 
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entoman

wildlife photography
May 8, 2015
325
332
UK
btw sigma EF lenses work just fine on the R5 with the adapter.. I've several, no issues on any of them
Yes, *any* EF lens should work fine on RF mount cameras, using the Canon adaptor. At least, that’s the theory.

In practice, some will acquire focus as rapidly as Canon glass, but others will be slower and more hesitant, due to heavy elements and/or less efficient focus motors.

Tracking subjects across the frame, at a near-constant distance, should theoretically be as good as with Canon glass, as it is dependent on Canon’s tracking algorithms, rather than an ability to refocus. However, AF and tracking both utilise cross-talk between chips in the *lens* as well as the body, so third party lenses may not track quite as efficiently, especially when using eye-AF.
 

unfocused

EOS-1D X Mark III
Jul 20, 2010
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...My guess is that they are delaying release of such lenses for 3 reasons:
  • they want to design new lenses to take advantage of the shorter flange distance.
  • they can barely keep up with demand for their existing lenses.
  • Supply chain issues (chips etc)

I'd add a fourth to that list: Cost/Benefits

Sigma offers a mount exchange service that allows you to send in a Canon mount lens and have it changed to Nikon mount (for example). That implies that everything beyond the mount is identical in their lenses. I don't know if that will be possible with mirrorless lenses. If, as you suggest, they may want to, or need to, design lenses specific to the RF mount then they may be waiting until they see sufficient demand to justify the expense. Canon's R cameras seem to be selling well, but we really don't know how well. Selling a third party lens that is specifically designed for one mount means a lot fewer sales than one lens that can be used across all the brands.
 
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snappy604

EOS RP
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Jan 25, 2017
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Yes, *any* EF lens should work fine on RF mount cameras, using the Canon adaptor. At least, that’s the theory.

In practice, some will acquire focus as rapidly as Canon glass, but others will be slower and more hesitant, due to heavy elements and/or less efficient focus motors.

Tracking subjects across the frame, at a near-constant distance, should theoretically be as good as with Canon glass, as it is dependent on Canon’s tracking algorithms, rather than an ability to refocus. However, AF and tracking both utilise cross-talk between chips in the *lens* as well as the body, so third party lenses may not track quite as efficiently, especially when using eye-AF.
that's always been the case.. likely due to reverse engineering.

however I use a sigma 150-600C just fine on the R5 for birding with the adapter.. and I use the sigma 30mm ART, 20mm ART, etc without any tracking issues. To be honest don't find it significantly slower than my RF 24-70 2.8L and that is one of the cringe worth prices.