topic C300 Mark III Registers lens data, but cannot communicate with any lens functions (IS, AF, Servo) in Professional Video

C300 Mark III Registers lens data, but cannot communicate with any lens functions (IS, AF, Servo)

bearwalk — Thu, 20 Mar 2025 02:05:20 GMT

Hi there,

I just bought a used C300 Mark III (EF Mount) - and it's basically mint with this one major exception. Autofocus won't work, Image Stabilization won't work, Servo won't work, nor iris. Strangely, I can adjust the iris using the menu, but it doesn't have any visual effect on the image.

Lens data is transmitted to the camera. I can see an iris value, focus guide, and focal length.

I've tried the CN-E 18-80mm T4.4, 70-200mm F2.8 L II, 24-105mm F4 L, 50mm F1.4, 35mm F1.4 L (all native Canon EF glass)

The above all work on both of my Canon R5's with the Canon RF-EF Adapter.

I've also tried delicately cleaning the lens contacts, resetting the original settings, and updating to the most recent firmware. I've also made sure all AF switches are thoroughly switched to AF and that settings in camera are set properly.

Any thoughts? Thanks in advance!

Re: C300 Mark III Registers lens data, but cannot communicate with any lens functions (IS, AF, Servo

shadowsports — Thu, 20 Mar 2025 02:31:17 GMT

Greetings,

Where did you purchase this camera? Do you have the right to return?

I'm not trying to nix your purchase but those are some huge hurdles to overcome. Me personally, I think I'd return it and continue shopping.

The only other option I see is Canon support for inspection and repair. If the behavior continues after a factory reset, and with multiple lenses, I suspect something is very wrong.

Re: C300 Mark III Registers lens data, but cannot communicate with any lens functions (IS, AF, Servo

bearwalk — Thu, 20 Mar 2025 12:52:19 GMT

Hey there Rick,

I purchased from a seller on eBay - I know, not the most confident of purchases, but the seller seems like he wants to do what's right. I figured I'd troubleshoot for a little bit and if I couldn't find a solution, he'll accept a return.

I was just hoping there were 1 or 2 more things I could try before throwing in the towel.

Thanks,

Brian

Re: C300 Mark III Registers lens data, but cannot communicate with any lens functions (IS, AF, Servo

shadowsports — Thu, 20 Mar 2025 15:05:10 GMT

Hi Brian,

By testing with multiple lenses and performing the main settings reset, you've done everything that could be expected😄.

I suggest walking away. There will be other deals.