EOS R6 Mark II requires multiple shutter presses to focus in low light

[LifelessLewis]

Hey, I have a Canon R6 Mark ii with an RF 24-105 L f/4. I am using spot autofocus with no tracking in one shot mode. Sometimes in low lighting it will fail focus on something with slightly low contrast. However, if I half press the shutter a few more times it will eventually focus, showing that it can manage it at the point I'm trying to focus on.

I have ensured that the Lens drive when AF impossible is set to continue focus search. However it's like it doesn't actually search the full focus range to even try, just decides that it can't focus without actually trying. Is there a way to force it to search the full focus range before deciding that it's out of focus?

Thanks.

[LifelessLewis]

I understand all that, But thanks for the details and screenshots, will use a speedlight and see what I get.
I'm just most confused why It doesn't even try though, think about this for a moment. If the lens is as out of focus it can get, then obviously there's no contrast for it to detect, even if the subject at least has some contrast. In my mind (and this is where I may be thinking wildly incorrectly) it should at least scan the focus range to attempt to find focus, if it did that, then once it got near focus I know that it would pick up enough contrast to actually be able to lock focus.

Forgetting everything else, does what I'm saying there actually make sense? Because to me, it logically should do. My old 6D and 6D mkii and very other DSLR all did this, I know where are fundamental differences but still.

[deebatman316]

It does try. In One Shot it will try and focus then stop. Then try again to acquire focus. It doesn't constantly keep trying and not stop like Servo AF. "In my mind (and this is where I may be thinking wildly incorrectly) it should at least scan the focus range to attempt to find focus, if it did that, then once it got near focus I know that it would pick up enough contrast to actually be able to lock focus." Doesn't work that way even if you try and manually focus close to where in focus is. If its still lack of contrast it still won't lock focus even if its close. The camera still see lack of contrast. DSLRs work the same way no contrast even if close to focus still not going to lock focus without an AF Assist Beam. "I know that it would pick up enough contrast to actually be able to lock focus." If the lighting situation is the same that doesn't change how the AF system works. What Canon branded Speedlite do you own. How do you know its not scanning through the entire focus range. RF lenses don't have a focus distance scale on the lens like EF lenses.

[LifelessLewis]

Ok, so I know it's not trying the full focus range, because I can physically see it not really try to change focus through the viewfinder. As in I can't see it change focus much, it doesn't change through the full focus distance from near to far in order to try and find the contrast to lock onto.

So it will just change to a red square and stop trying, however if I engage the AF again it might get a little closer, then after an arbitrary amount of tries it will eventually find enough contrast to actually try and manage to lock onto.
I'm not with the camera at the moment, But I think I even tried it with servo and it just came up with the red square too, again without trying to focus through the range of nearest to farthest to try. I think my flash is a 430ex, might be a 430exii but I'm not with it to be sure.

I will try to find time to get it on a tripod and take a recording of what I see happening if I can find time during the bustle of Christmas.

Thanks.

[deebatman316]

Your camera is working correctly DSLRs work the same way. If the AF system is way out of focus it will never get close this is even true with DSLRs. The camera focuses wide open so the depth of field always stays the same.

[Waddizzle]

Be cognizant of the lens’ MFD, minimum focus distance.  This specification describes the minimum distance to the subject.  Move closer than the MFD and the lens will fail to focus.  

[EDIT]
The MFD spec only applies to the shortest focal length for a zoom lens.  As you zoom out to longer focal lengths, the MFD will increase by a significant amount.

[LifelessLewis]

Yeah the thing I'm trying to focus on is about 3-4 meters away, definitely not something as simple as that haha.