EOS R8 won't autofocus with Sigma 50-500

[tiburon7227]

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 🙂

[deebatman316]

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

[Tronhard]

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. 

[Waddizzle]

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.