I recently picked up a Canon EOS RP. The bundle came with an EF adapter, making a boatload of great, affordable glass available. Great, affordable glass means nothing if the adapter does not perform well.
How Well Does The Adapter Work?
Canon grants modern mirrorless focusing functionality to DSLR lenses. All focus modes are available along with face/eye detection through the viewfinder. All 4779 phase detection focus points are available. I compared back to back with an RF lens and I noticed little difference in performance and functionality.
Feel and Balance:
The adapter is very well made and rigid with no apparent flex. All the lenses tested feel well balanced and no more front heavy than native RF glass would be. I highly recommend the bundled grip. It makes for a terrific handling experience, especially with longer lenses.
Just like stills, video focusing works quite well. Accurate and quick with little to no hunting and smooth transitions from focus subject to focus subject. Any video limitations have more to do with the RP, like crop 4K and limited fps options, than adapted lenses. But if you are looking for solid, straightforward 1080p full frame video the EF to RP adapter worked quite well.
Dust and Water Resistance:
The adapter is dust and water resistant which is good news for those adapting weather resistant lenses to the weather resistant RF bodies.
Compared to RF Glass
The Canon 50mm f/1.8 EF STM is very affordable and works very well on the RP. The current RF mount options closest in focal length and spec cost quite a bit more and while fine performers, I prefer the 50mm STM. The 50mm f/1.2 RF L is in a different performance class admittedly, but costs a lot more and is larger than I would like a 50mm lens to be. The 35mm f/1.8 RF IS Macro STM is more reasonably sized and priced, but even with the IS and macro capabilities I am just fine with the EF 50mm f/1.8 STM. The older non-IS Canon 70-200mm cost me far less than $1,000. If you would like some IS action one of those can be had for a bit more. When Canon does release their 70-200mm f/2.8 RF variant I expect it will have IS, but also be quite a bit more than either listed above.
The RF 35mm f/1.8 IS Macro STM is almost exactly the same size as the 50mm STM EF lens w/ adapter. I have tested a large number of EF Canon lenses (8-15mm f/4L, 16-35mm f/2.8 L, 17-40mm f/4 L, 85mm f/1.2, f/1.8, and SIgma Art, 17-40mm f/4 L, etc.) and none felt out of place on the RP.
The new Canon RF lenses are stellar performers, but most cost way more than the RP. Canon has done a fantastic job here with the EF to RF adapter, so not being able to afford the new RF glass is not an issue. There are other mirrorless system options that allow adapting legacy glass, most similarly Nikon DSLR glass w/ the Nikon Z bodies for instance. However, none I know of cost less than the Canon EOS RP with EF adapter . This setup made for a very pleasing adapted lens experience and I recommend it highly.