RF mount inconsistent manual focus

[dave_baas]

I'm finding the "focus by wire" manual focus on Canon RF mount lenses inconsistent. Meaning, I mark with tape completely out of focus and pull back to just shy of infinity. But if I pull back and forth from these physical positions with the manual focus ring the actual focus the lens sees and measures shifts

For lenses without focus presets, how can I manage this and/or is there an explanation?

That said, are there any mechanical focus legacy lenses I could use on the r5 RF mount?

[rs-eos]

What specific lenses are you using?

Are you attempting to pull focus for video work?

[AtticusLake]

It sounds like you're trying to hit set forcus marks, maybe for video.  Unfortunately, this is impossible with fly-by-wire lenses -- any electronic lenses from any manufacturer.  The control ring on the lens is only an input wheel, like the scroll wheel on your mouse, and it has no hard stops.  So if you spin it past the end it keeps spinning, but the lens can't focus any farther.  So they get out of sync.

The solution is to us a manual focus lens -- i.e. an all-mechanical lens.  This is essentially what all the film-makers do.  Good news is that there are lots of mechanical RF lenses, and you can use EF, FD, or PL lenses with an adapter.  If your lens is all-mechanical, then electronic compatibility is not an issue, you just need an adapter which physically fits the lens to the camera.

[Waddizzle]

“ But if I pull back and forth from these physical positions with the manual focus ring the actual focus the lens sees and measures shifts. “

You lost me here.  Did you mean to say zoom ring?  Are you saying that the focus point is shifting as you change the zoom setting on your lens.

Help us to better understand your issue.  What lens(es) are you using?  I suspect you could be looking for the performance of much more costly parfocal lenses, commonly used in cinematography. 

https://en.wikipedia.org/wiki/Parfocal_lens