RF Lenses or EF/RF Drop-In Filter Adapter ?

neuroanatomist said:

There isn’t and won’t be. Lenses are designed for a specific flange focal distance (mount to sensor). That distance is 44 mm for EF and 20 mm for RF. The difference is why the adapter is needed. The product you’re suggesting would add extra space between lens and camera. Those products do exist (without a drop in filter) – they’re called extension tubes. Canon made them for EF, 3rd parties make RF versions. When used, they increase maximum magnification by allowing closer focus, at the cost of losing the ability to focus the lens on distant subjects.

Just as an example, putting something the length of the EF-RF adapter behind the RF 70-200mm lens, you'd have the convenience of being able to drop in a CPL or ND, but you could not focus the lens on anything further away than 2 m from the camera. Would you want a product like that?

There are products designed allow filters behind the lens by fitting a bit into the camera body (for both EF and RF), usually used by astrophotography folks. But those do not allow use of a CPL that needs to be rotated.

If you switch to RF lenses, you're back to moving a front CPL from one lens to another, although if you pretty much always use a CPL, an alternative would be to have one for every lens.

I do understand your dilemma. I have both the plain EF-RF adapter and the DI version (with both CPL and vND filters, and the clear filter when I don’t want to lose light). For my EF 11-24/4 and TS-E 17, the front filter options are very inconvenient (dinner plate size filters for the former that I don’t have, salad plate sized filters for the latter that I do have and are a PITA to carry and use). There is rumor of an RF 10-24/4, but I don’t think I would give up the convenience of the drop in filter for an extra millimeter on the wide end. Similarly, there is rumor of an RF TS 14mm – that would be a tougher decision and honestly I’d probably buy such a lens but keep the TS-E 17.

For many of my EF lenses where there’s an RF option I switched, e.g., EF 16-35/4 to RF 14-35/4, EF 24-70/2.8 to RF 28-70/2 (I had the RF 24-105/4 from when I bought the R to try out the system, but I didn't fully commit to RF until the R3 came out), EF 70-200/2.8 II to RF 70-200/2.8. The improvements were worth it to me – the extra 2mm on the UWA wide end keeping the same 77mm filters, an f/2 standard zoom, the more compact 70-200 with better IQ. For other lenses, I did not switch. The RF 100/2.8 Macro goes to 1.4x mag but has focus shift, so I kept the EF 100/2.8 (if I want higher mag, I have the MP-E 65 1-5x for which there's no RF equivalent and likely won't be for a long time, if ever). I kept the EF 600/4 II, because the RF 600/4 is essentially the EF 600/4 III with a permanent adapter, and the II to III update for EF made the lens lighter but not optically better (I can handhold the EF 600/4 II already). I kept the EF 85/1.4L because I just don't use it enough to justify swapping it for the RF even for the extra half-stop(I previously had the EF 85/1.2L II, so I know what I'm missing and f/1.4 is fine for my uses).

At the end of the day, it's a decision you have to make for yourself. I've been very happy with the RF lenses I have.

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