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EOS R8 won't autofocus with Sigma 50-500


I recently borrowed a Sigma lens from a friend that used it on their R6 body.  I have tried to use the lens with my R8 (and also my 60d) and it will not auto focus.  I get a red flashing box for my AF point when I try to snap the picture.  I tried the lens on both bodies so I am "guessing" it is the lens at this point (my other lenses work fine).  Any ideas on what to do here?  Yes, it will take pictures if i flip to manual focus and move the focus ring but the AF wont work.

Help 🙂



Older Sigma lenses don't AF on newer camera bodies. This is a lens incompatibility problem that Sigma will have to resolve NOT Canon.


Current Gear: EOS 5D Mark IV, EF F/2.8 Trinity, EF 50mm F/1.8 STM, EF 85mm F/1.8 USM, 470EX-AI & 600EX II-RT

Retired Gear: EOS 40D


Hi and welcome to the forum:
Sadly, there is no guarantee that Sigma EF lenses will work with Canon R-series bodies.  The 50-500 is an older model - released at least 14 years ago, and any inquiries about compatibility should be addressed to Sigma, given it is their lens.  Can you advise what EF-RF adapter you are using - what brand and model: that is your best hope. 

cheers, TREVOR

"The Amount of Misery expands to fill the space available"
"All the variety, all the charm, all the beauty of life is made up of light and shadow", Leo Tolstoy;
"Skill in photography is acquired by practice and not by purchase" Percy W. Harris


It is an older lens, but it should at least be able to fire the shutter.  Be cognizant of things like Minimum Focus Distance.  I do not recommend using a teleconverter with this lens.

I think the only time you should see red AF points is when the camera body is in AF point selection modes.

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