RF 200-800 does not focus when starting at 800 mm

[Chandan_k]

I am Using RF 200-800 with my Canon R5 Mark 2 . I was having plenty of Issues with Using AF -  However Most are resolved reading through guides & community reading. However , One Thing is Still Bugging :   When I start shooting Shutter Priority , and Start focussing after Zooming the Lens at 800( without aiming the Subject, I syaert with 800 straight , it Does not Auto Focus with Back Button or any Other mechanism. However, When I gradually start Focussing 500/600 and Zoom out to 800 , the Focus worked Fine and I got Good Shots.  Is this a defect in my Lens or this is the way , this lens behaves ? Any responses on this will be appreciated. 

[rgl47]

FYI Chandan, the issue I am experiencing seems to have started after I did firmware updates. But, even with the most recent updated from 11/20/2025, it did not fix the issue. As many pointed out, having the stop focus search on or off should not matter. I have not changed any of the settings from when it worked normal to now when it doesn't so unless the camera/lens has a mind of its own, it would not make a difference turning it off.

[rgl47]

https://community.usa.canon.com/t5/EF-RF-Lenses/Canon-RF-100-400-Autofocus-problem/m-p/407856#M25405

Here is another post from about 3 years ago with similar issue.

[vantage]

@Chandan_k

As I posted earlier, my RF 200-800 with my Canon R5 Mark 2 doesn't exhibit that behavior anymore. If you'd like, I can post pics of all my autofocus menu settings, you can set yours the same way and see if the problem lessens/goes away.

On the last page of the camera AF menu settings (page 7 of 7 ) is a URL to "AF Setting Guide URL."

[rgl47]

Thank you, Vantage. I don't use my R5ii with the RF 100-300 f/2.8. Instead, I use the R1 and sometimes the R3. I didn't realize only certain cameras work correctly with that lens. I will however check out the url. As I mentioned, I've had my settings the same for about 14 months so for the lens to start acting up only in the last 2 months, doesn't make a lot of sense for it being AF settings. Maybe you can send me the settings anyway to double check where the issue may be?

[TomRamsey]

I use the lens with an R6 Mark 2 (always on shutter priority) and I have never experienced that problem.  

[vantage]

Here's my AF settings on my R5 II. As I mentioned, I haven't seen the "does not focus" problem on my RF 200-800 for quite a while. I tried several different shots this afternoon starting at 800mm and it never failed.

Camera mode : P
Lens "Control" switch: Fully forward (AF)
Lens stabilizer switch: On

[Chandan_k]

Thanks. I will Use your settings and est that . Though I always Keep Eye Tracking ON When Doing animals and same for. Subject to Setect ON as Animals . However I have Observed Some other Settings Which I will try Now . Shall Provide a Feedback . Cheers 

[rgl47]

Thank you, vantage, for sending the settings. Although for sports and action, I use different basic settings. I don't see anything that stands out in your settings that would make a difference in my case/issue and some are the same on my end.

[vantage]

@rgl47,

Understood. If you're still having the problem, it may be worth duplicating my settings to see if your problem goes away. If it does, we know it's some combination of settings that causes the problem and eliminates it.

[Chandan_k]

The Camera Firmwire is 1.1.1 Jukly 25 Released Latest Update . I am not sure 1.2.0 applies on R5 MK 2 .... ?