EOS R5 with RF 800mm lens can't focus on birds in flight

[ruthlessrider]

I have a Canon R5 that I am trying to shoot birds in flight (eagles) with with the Canon RF 800mm lens. The lens seems to see the birds fleetingly, but does not fully focus before losing the birds completely. As I move the visual field around trying to “find" the birds, as they cross the field of view they momentarily appear and then again disappear from the filed of view. Nothing I have done so far seems to work; I have tried manual focus, adjusted the full vs 20m- infinitely setting, and turned the stabilizer on or off. Nothing seems to work. If stationary, no problem. Looking for any solutions. 

[ruthlessrider]

Just to add to the question: Is it the Lens or the camera?

[kvbarkley]

Hard to say. 800mm on a bird in flight is tough. I think it would be easier with the viewfinder rather than the LCD on the back.

I usually pre-focus on a tree or something, but if you hit the focus button on a blank patch of sky, who knows where the focus ends up.

[p4pictures]

Hi Ruthlessrider,

I have a couple of questions for you…

1. Which AF method are you using?
2. Do you have the camera subject to detect set for animals and with eye detection on?

EOS R5 can only do subject detection when set to face + tracking AF, or one of the zone AF methods. Eye detection only works when using face + tracking AF method. 

When using the RF 800mm F11 lens there is only a central area of the frame - about the same size as the square zone AF area - that is usable, if the bird is outside this area it cannot be focussed on using the subject detection.

[ruthlessrider]

Aha! just found the solution after reading, of all things, the manual. I disabled the continuous focus in AF menu 1 and I am again able to focus on moving objects like bird in flight.