Sony a7R III to the a7R II a7s AF accuracy and speed?

[haring]

I am just wondering how fast and accurately the a7R III, to the a7R II an the a7s focus with third part lenses like Canon and Nikon?
Are they usable for wedding? Is there anybody who used these mirrorless cameras for wedding with third party lenses...
Thanks so much!

[gstark]

Remember that with a mirrorless camera, you have have no optical viewfinder. Typically, just a video viewfinder affixed to the rear of the camera body.

Consider how easy that sort of a viewfinder will be to use in bright sunlight, with glare and ambient light making the viewfinder difficult, if not impossible, to use.

I haven't had an opportunity to use either of these bodies, although my son is currently using a Sony mirrorless and keeps it with him constantly to shoot images of my 5 month old (today) granddaughter. The OOC mono shots are very bloody nice.