@Waddizzle wrote:
"Good luck. You're correct. I have no idea what you have been describing. I think that it should be impossible for a lens to refocus when the AF/MF switch is set to MF. But, you're saying that it refocuses."
What I gathered is, as his main complaint, he can't get the R5 to auto focus on a hummingbird when using a remote trigger and his conclusion is that the AF in the R5 isn't working properly. Then, to remedy that, he is trying to pre-focus on a spot manually (lens in manual mode) where he thinks the bird might be at some point. So at some time, after pre-focusing the lens, the R5 goes to sleep or powers off while he is waiting. Then when his target appears he wakes tha R5, takes the shot with his RT, and manual focus has been re-set, i.e., his target area is no longer in focus and all he gets is a blurry shot.
Now, my DSLR's do retain manual focus on an object when switched off then back on, like if you are on a tripod, manually focus on a subject, then turn your DSLR off. When you turn it back on, that subject will still be in focus, just like you left it. With our R6, if you do that, focus is re-set to minimum focus distance and not where you left it. I know this because of this post and it's not something I would do or have ever needed to do, just to be clear.
I made a long winded reply to this threead late last night, with images, and decided to delete it because it didn't really answer the OP's concernes. I've been remote shooting hummingbirds for quite a while, but have never used a remote trigger. Instead, I use either a 15' plain USB cable or 30' USB cable with a repeater, and either the EOS Utility or Helicon Remote, depending on which laptop I'm using. My wife uses WIFi or Bluetooth with the R6, I'm not sure which. I prefer USB because it is more resposive, at least with the 5D mark IV and 7D mark II. With the utilities, you can focus with a mouse click, or if you have a touch screen, a finger while in live view. But you know that 😉
Shot using 30' USB cable w/repeater and EOS Utilty.
Yup! I just tried 3 different lenses - 2EF and 1RF lens - focused manually, then I shut the camera off, turned it back on, and it was focused on the exact spot as when I shut it off.
As per Christoph Walz's famous line in Inglorious Basterds, "That's a bingo!" I'll look back at the thread as I seem to recall that too, but it seemed to be related to something else. In any event, that's the solution! Thanks to all who paticipated and cam eup with this solution. What a weird inscrutable meaning title of a function though. Reading page 829 in the advanced users manual, one would have no idea this is related to this subject, or really to what it was really talking even in reference to some issue with "gear-type STM lenses." Why/how this would be related to this problem?
In any event, problem solved. Now I'll make some notes in the PDF for next time.
Thanks very much to everyone!!!!!!
Yes. 
That is exactly correct. To the letter! Thank you. Thank you. And nice images!
Shooting wild life, time lapse, or any such similar situation, the camera will go to sleep after a certain period of time while you are waiting for the "right moment." As anyone who shoots wildlife knows, wildlife is skittish. You just don't stand in front of your camera waiting for (who knows how long) for something to happen so you can push the shutter button on the camera. That's why they make remotes.
Therefore, the issues remain:
1) With a 5d MKIII, I set the camera up, pre-focus manually - and just so no one makes a wrong assumption, the lens is set to "M" - and when the bird, squirrel, woodpeckers, mountain lion, bear or what have you comes along and I am a safe (or, depending on the critter, very safe) distance away, I push the button on the remote and the 5dMKIII wakes up, takes a photo, focused on exactly the same spot where I last focused it before it went to sleep.
2) The same lens on the R5 in the same situation with the same settings on the same tripod turns out wildly blurred out of focus.
3) Therefore, it is not the lens, it is the camera.
Having said that, the cause of the problem then can only be one of four things:
a) the lens is broken. (But it is not as per working fine above and, previously, the same issue is with all my EF and R lenses on the R5) Eliminating that then, three remain:
b) there's a bug in the camera circuitry or software;
c) the Canon engineers just didn't even think about this and there is no function to preserve Manual Focus settings, thus proving once again Ansel Adam's famous dictum;
d) there is a setting or group of settings among the thousands of combinations of settings in the camera you must use and if you don't, the default causes the camera to defocus upon waking and there is absolutley no information on that in the manuals (or at this point, it seems, on the web.)
Now you, FloridaDrafter, seem to be saying that your R5 does retain its focus, in the above situations, so that would lead me to believe "d" above is the issue, and you have apparently obtained the secret sauce... I gratefully in advance ask then, what are your settings?
Thanking you again, and in advance...
PS: Attached are two images. These I would have to say were "lucky" (I have a bunch of "lucky" shots, but I'd prefer to be deliberate rather than lucky...) although the first image suffers from a lack of sharpness due to focus issues.
