topic Re: EF to RF adapter for Canon EF 100-400mm f/4.5-5.6L IS USM: R10 in Gear Guide

Will EF 100-400mm lens work as well on EOS R10 via adapter as on EOS 90D?

RayboyUSMC — Fri, 21 Mar 2025 13:43:46 GMT

I just bought a used Canon EF 100-400mm f/4.5-5.6L IS USM to use on my D80. I am thinking of upgrading to a D90 or and R10. If I go with the R10 and use the EF to RF adapter, will it work as well as the lens would on the D90? My experience with mirrorless cameras so far has been very good and I would like to try the Canon mirrorless R10. Almost all my shooting is on birds in my back yard to include Hummingbirds where I use a fast shutter speed and the high shooting speed. I am an advanced beginner.

Re: EF to RF adapter for Canon EF 100-400mm f/4.5-5.6L IS USM: R10

deebatman316 — Fri, 21 Mar 2025 00:57:10 GMT

If the lens is the original push pull EF 100-400mm F/4.5-5.6L IS USM lens it won't fully support the highly advanced AF systems found in both cameras. It won't support 12 fps and the AF motor may not be fast enough to keep up with moving subjects. That lens isn't fully compatible with Continuous High Drive shooting. It should work fine though. I wouldn't recommend investing in a DSLR as they have been discontinued along with EF lenses. If the lens can't keep up with high fps the camera will automatically slow down to compensate. In terms of specs the EOS R7 would be closer to the EOS 90D over the EOS R10. The EOS R10 has a shorter battery life than the EOS 90D. The EOS R7 & EOS 90D both use the same LP-E6 series batteries unlike the EOS R10 which uses the LP-E17 battery. Which is mainly found in Rebel series cameras. But keeping extra batteries on hand shouldn't be a problem. The EOS R7 also offers IBIS (In Body Image Stabilization) for lenses that don't have IS (Image Stabilization) and it works in tandem for lenses that also have IS (Image Stabilization). If adapting stick with the Canon brand EF-RF Mount adapter. 3rd Party EF-RF Mount adapters are nothing but trouble and cause problems.

Re: EF to RF adapter for Canon EF 100-400mm f/4.5-5.6L IS USM: R10

March411 — Fri, 21 Mar 2025 01:02:55 GMT

Rayboy,

Overall EF glass will perform better on an R body simply due to the advancement in technology. Just a couple of comparisons of the bodies. Number of Focus Points on the R10 is 651 verses 45 on the 90D. The R10 uses the Digic X image processor and the 90D uses the DIGIC 8. The X is the superior and more capable processor and the sensor pixel area is about 33% larger pixel larger on the R10. The 90D does have a 33MP sensor verses a 24 on the R10 so you will have less latitude for cropping. The R10 has eye tracking, 90D none.

If you purchased the EF100-400mm f/4.5-5.6L IS II USM is does support maximum continuous shooting speed on the R body. Also the end of service for the EF100-400 4.5-5.6L IS II USM remains as undecided so you have at least a year or two for Canon support.

Re: EF to RF adapter for Canon EF 100-400mm f/4.5-5.6L IS USM: R10

deebatman316 — Fri, 21 Mar 2025 01:19:19 GMT

I think the OP may have purchased the original push pull model. I’m waiting for them to confirm that. If it is the original or version II model. If it’s the original then it’s no longer supported by Canon. The original version was discontinued and replaced in 2011. It also won’t be fully compatible with either camera. But it will work with limitations though.

Re: EF to RF adapter for Canon EF 100-400mm f/4.5-5.6L IS USM: R10

March411 — Fri, 21 Mar 2025 01:32:06 GMT

Agreed, if it is the push model that would be a challenge and would limit functionality.

Re: EF to RF adapter for Canon EF 100-400mm f/4.5-5.6L IS USM: R10

RayboyUSMC — Fri, 21 Mar 2025 02:39:11 GMT

Thanks for the information. Not like the days when my first camera was a Brownie Hawkeye. It is the push pull lens.

Re: Will EF 100-400mm lens work as well on EOS R10 via adapter as on EOS 90D?

ebiggs1 — Fri, 21 Mar 2025 14:33:37 GMT

" If I go with the R10 and use the EF to RF adapter, will it work as well as the lens would on the D90?"

To better answer you question, yes, it will work as well as it did. The fact most responders make is it won't take advantage of all the new features of the nes camera system and that is true. However, if you never needed them and don't necessarily want them there is no reason why the les won't work as expected. Of course as you grow you may want to take advantage of some advanced AF settings and then you can decide to buy an RF series lens.