1Dx III VS R3

[HDNitehawk]

I have the 1D IV and it was always faster than any of the 5D body's. I always contributed this to the battery power. I actually ran comparisons on the my 500mm and the 1D IV with a timer. On smaller lenses speed was never noticeable but hit rate on in focus pictures was always higher by several %.

I would expect similar for the R5 vs the 1Dx III.

However the first lens I tried on my R5 was the EF 35mm f/1.4L II. As you know the lens is great because of the critical focus between 1.4 and 2.0 and the interesting bokeh it generates. It did great for me, but I only used it a few days.

Another lens I tested on the R5 was the EF 180mm F/3.5L Macro, and I thought it was much quicker to focus than it did with the DSLR bodies. I was actually somewhat impressed. The lens had a reputation of being very slow.

So far the critical narrow DOF focus I thought has been good.

Did you compare the EF and RF 85mm on the R5?

Not to doubt what you are saying, but I would put both lenses on the R5 and do a chart test in MF wide open to make sure it isn't a lens issue.
Or even just a simple comparison of walk around shots on the R5 with the EF 85mm and an adapter.

[Fast Glass]

But, I'm EXTREMELY curious now after this conversation to try and rent an R3 for a direct comparison.

I do have a date to go with my buddy to do a direct apples to apples comparison with all my lenses and his lenses with the 1Dx III and his R5. And record the results along with possibly a video of it. My first hand at video making.

Because I don't feel like an extremely exhaustive comparison has ever been done.

[Fast Glass]

I did with my friends R5. Same results.

Now, I do realize this is a very narrow circumstance with me asking a lot from the AF. 85mm at f/1.2 is EXTREMELY narrow the DOF and we are talking about a very small margin of error. Basically none.

But I agree, I have been trying to rule out things like lenses not focusing correctly or bad samples. I do not want to put something down do to it not focusing correctly.

Just for reference though, my own personal 85mm f/1.2 II is dead on focus with two 1D III's, a 1Ds III, two 1Dx III's, an R5, EOS RP, 60D.

So it's not impossible for it to not behave with a particular body. But I'm fairly confident if there is a mis focus issue it probably be with the body in question.

But the results are the same with two copies of the RF 85mm f/1.2 on two separate R5 bodies, on a R6 and RP.

Anything could happen, I won't dismiss anything.

This is a matter of millimeters. It's not like we are talking about huge differences. But it's just one of those things like you said. It could be taxing what a 5-series AF can do.

Now, I never did broad day light, it was either well lit indoors, dim indoor or cloudy outdoor with it being the last half hour of the day.

It could be in good light it performs better. But mildly dim lighting is a frequent situation for me. So not exactly usable. Part of the reason for a extremely wide aperture for me.

[Jonathan Huyer]

Thanks for the additional details. When you're using the 1DXIII with the 85 f/1.2, what focus mode are you in? I'm presuming servo, with all the focus points activated and auto-select with people priority? In other words, the camera looks for people in the frame, and moves the focus point automatically. Is that correct? I know the 1DXIII does that very well, but it can't do eye-detect AF unless you're in live view mode. So I'm curious if you're using the optical autofocus (mirror down), and still getting accurate eye focus (better than the R5). Or, are you manually selecting a focus point, and moving it over the subject's eye yourself?

[Fast Glass]

@Jonathan

With the mirror down the 1Dx III doesn't fair any better than the R5 from my experience. And this happened with me and the Sigma 105mm f/1.4 and the 1Dx III, live view AF, with it's ridiculously thin DOF. Although if I remember correctly it was much less problematic than the 85mm. Something that didn't seem out of line. This was a year ago.

I know we tried it with a couple settings, AI servo and AI focus. And others.

Fixed focus points definitely better though, not as much in the accuracy department. But more so it not hunting for the eye, especially with a mask which totally messes with it. I guess it's not that relevant in practice, since anyone I photograph is not wearing a mask. But the 1Dx III doesn't have that issue.

I'm also thinking the Dual pixel AF is focusing on contrast in one plain vs two in the 1Dx III or even a ultra sensitive X type AF sensor. Correct me if I am wrong though.

Soon enough I'll be doing a super detail analysis of the two AF systems since the R5 is such popular camera. I think it is very relevant. Along with the R3. Which I have much higher hopes being more fine tuned.