Aperture communication issues between Canon EOS R8 and sigma 150-600mm f/5-6.3 DG OS HSM C

[Patrickcm03]

Recently I have been noticing some autofocus issues with my Canon EOS R8 but only with my telephoto lens: the Sigma 150-600mm f/5-6.3 DG OS HSM Contemporary. I have been doing some troubleshooting over the past week and pinpointed that it was most likely an issue with the lens. There is an issue with the aperture communication between the sigma lens and my r8 as the autofocus works with the lens from 150mm to around 300mm but stops working above 300mm, right around where the minimum aperture changes to f/6.3, yet it shows a minimum aperture of f/5 even at 600mm. Both the lens and body firmware are up to date. I don't think the issue is the canon ef to rf adaptor, as the af worked well through the entire range of my Canon EF 75-300mm f/4-5.6 properly communicating a change in minimum aperture.

Has anyone else noticed this issue with this lens with other mirrorless cameras? What are some recommended steps for a fix?

[kvbarkley]

I think you might be seeing an unintended effect of it being an EF lens. The Sigma lies about its aperture to the camera so the camera does not just give up and stop autofocusing. This is not needed in the R series, but the lens does not know it is connected to the R.

You might see if there is a new firmware update for your lens.

[ebiggs1]

You have the Sigma dock to check the FW? If not get it. You need to check the lens on a different camera preferably a DSLR. If you have the Canon brand adapter there is almost no chance it is the problem.

First thing when something like this happens and you have no reason why is to fully reset the camera. Make sure you have fully charged batteries.

Sometimes big zooms have a problem with AF because or various reasons so a prefocus can remedy that. Get the focus close manually and then try AF.

[Patrickcm03]

Firmware is up to date for both the lens and the body. I have the sigma dock and reset the lens to default settings recently. I also reset the R8 settings and just updated its firmware. I checked the lens on my old dslr and it couldn't lock focus onto anything at those focal lengths. Recently, I have been focusing manually and as soon as I use af it looses it and searches again until it settles with an orange box and the whole image is out of focus.

[March411]

I used the Sig 100-400mm and 60-600mm (it was a beast) and had the same issues but the firmware update resolved the pulsing/racking on both lenses but it was on the R6 Mk II. Have you reached out to Sigma USA or Canon yet? They were both real helpful in getting my challenges resolved. 

[LeeP]

"The Sigma lies about its aperture to the camera so the camera does not just give up and stop autofocusing."

I learned something new today. The "lie" is such a clever work around.

[shadowsports]

@Patrickcm03,

I noted you said both the camera and lens firmware was up to date in your opening post.

I owned this lens for a couple of years.  I don't recall the aperture being misreported in exif data when adapting this lens to my R5 C.  I also didn't experience focus pulsing which was reported by many R7 owners using this lens for Wildlife.  Some of these problems were caused by use case.

Based on what I've read, there's nothing that can be done since the incorrect info reported in the EXIF data is caused by a communication issue between the lenses older chipset and newer (faster) mirrorless communication standards.  

The lens is in fact shooting at f6.3 when the focal length is set above 380 mm.  This is a physical limitation of the lens regardless of what the EXIF data shows.  I don't think there's anything you can do unless Sigma releases more firmware.  Since the lens is 12 years old now that likelihood is low.

[March411]

These may come in handy

• Canon USA: 800-652-2666
• SIGMA Corporation of America: 631.585.1144  

[Waddizzle]

“ I think you might be seeing an unintended effect of it being an EF lens. The Sigma lies about its aperture to the camera so the camera does not just give up and stop autofocusing. “

True that! The aperture is F6.3 at 600mm. With a 1.4x teleconverter, that’s an effective aperture of F8.8.  Most DSLRs drop automatically focusing at that point.  Remember, the camera auto focuses at the lens minimum aperture setting.

Many DSLRs (Rebels) will stop auto focusing at anything over F5.6.  So the lens lies to the camera. Tamron lenses do it, too.  

[ebiggs1]

“I also reset the R8 settings and just updated its firmware.”

The camera FW will have nothing to do with this. Canon doesn’t update FW to make off brand lens models work on their cameras. The reset could that’s a good thing.