Hey folks,
I'm curious how good the M50's continuous AF works while looking through the viewfinder ? If i used an EF adapter and the 100-400ii, is the AF-C as good as say the 80D? I usually shoot single point AF and point it at the subject (wildlife).
Thanks
AF of the M50 is very good in low light, but it just hates back lit situations. An 80D might better perform in back lit situations.
I don't use long lenses like you do. I do shoot apertures like f/1.8 or f/2.0 using single point AF and touch&drag, especially when face tracking is struggling for some reason (low/back light, faces turning away often). The single point AF frame is small enough for me. The small single point AF frame does not feel larger than a 70D AF point. Focusing like this is better than using off center single point AF on my 70D. Using touch&drag is smooth and fast enough (generally a bit faster than switching AF points on my 70D), but more often than i would like it has a black out. You will have to get your face from the viewfinder and back to get it working again when this black out occurs. For my use this is not such a big deal as i can live with Face tracking in a lot cases too, but it gives me i pause in recommending the M50 over the 80D with that lens and what such a lens is generally used for.
If you always want to get the shot no matter what, i would go with the 80D or even the 7DmkII.
If it is o.k. to miss a shot occasionally (something i would estimate like not more than 2% of the times) because of this touch&dragAF black out, the M50 can do the job just like the 80D, maybe a bit better as moving focus points is generally a bit faster. Coverage of the frame by AF points is also very good with the M50

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Maybe for your use the best set up might be using the whole screen for touch&drag AF, choosing absolute in stead of relative, and just flip out the screen to prevent "nose focus". I never used touch&drag this way, but it might be better for your use.
Beside AF, (sorry for the off topic) make sure you can live with the EVF. The EVF is good. I don't experience any lag or something. But using an EVF it is sometimes impossible to judge if a shot will get a beautiful result or not, especially with bright sunlight. An OVF is better in this way, and the OVF adds more to your shooting fun because of this.