SHWeiss

I do not understand the physics here:
Camera canon RP (full frame mirrorless)
Lens: rokinon 14mm f/2.4 SP canon ef mount
Adapter: VILTROX EF-EOS R Auto Focus Lens Mount Adapter

First I tried a two sigma ef mount lenses with the camera/adapter and they focus to infinity, the rokinon would not focus past 5 feet. I tried the rokinon without adapter on a 5d mark 2 and it focused to infinity.

So please explain why focus is off when all 3 components function fine independently?

Thanks
Steve

billnikon Loc: Pennsylvania/Ohio/Florida/Maui/Oregon/Vermont

Here you go, here you can chat with a Canon tech. I am sure they would love to help you out. And they know much more than any talking head here.
https://www.justanswer.com/sip/justanswer?r=ppc|ga|26|US%20-%20Tech%20-%20Canon%20-%20Google%20-%20Alpha%20-%20Desktop%20-%20Broad|canon%20com%20-%20Alpha%20-%20Desktop%20-%20Broad&JPKW=canon%20company&JPDC=S&JPST=&JPAD=315288958744&JPMT=b&JPNW=g&JPAF=txt&JPCD=20181127&JPRC=1&JPOP=TM_Top1K_KWs_Set5&cmpid=958266695&agid=50216618760&fiid=&tgtid=kwd-25068236&ntw=g&dvc=c&gclid=EAIaIQobChMIq4PR2O-27QIVMP_jBx0pLQE_EAAYASAAEgLzB_D_BwE

Bbarn Loc: Ohio

Deleted.

CHG_CANON Loc: the Windy City

Canon will tell you to purchase a genuine Canon EF to RF adapter and genuine Canon EF or EF-S lenses. Otherwise, discuss the issues with the third-party vendors Rokinon (lens) and / or Viltrox (adapter).

It seems like the Viltrox adapter is behaving like an extension tube with the Rokinon lens. Do you mean it can't autofocus beyond 5ish feet? What happens if you just try to manually focus the lens on a further distance?

SHWeiss

It is a manual focus lens with a chip to control aperture electronically. I used a Canon EF to Sony E adapter on a Sony mirrorless FF camera and the Rokinon focused fine. So quite the mystery for the lack of focus with the Canon RP.

Blurryeyed Loc: NC Mountains.

I would say that you should have bought the Canon adapter but I don't know what is up with Canon because much of their gear is on Back Order including their EF to RF adapters.

JBRIII

I have a similar lens and a Canon adapter. In my case camera would not even register the lens was there. Had to tell camera to work even without a lens and then use manual focus.
My quest communication problem due to some change in the new system.

petrochemist Loc: UK

There is always slight variation in the length of adapters, this becomes far more critical with short focal length lenses (which 14mm definitely is).
Most adapters are made fractionally short to ensure standard lenses can focus to infinity (the focusing control going too far rather than falling short). I think this has proved to be an issue on all lenses I've tried adapting that were under 25mm. It is often possible to improve matters by adding a shim into the adapter to get the length closer to the theoretical value - I typically photocopy the face of the adapter, laminate the image & cut to size (including screw holes) then insert how ever many of the these shims are needed between the two halves of the adapter...