# Canon RF 400mm f2.8 L review by Christopher Frost



## Chaitanya (Aug 28, 2021)

Christopher Frost has posted review of RF 400mm f2.8L Lens.


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## neuroanatomist (Aug 28, 2021)

Chaitanya said:


> Christopher Frost has posted review of RF 400mm f2.8L Lens.


One could also check reviews of the EF version, since they’re essentially the same lens.


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## Jonathan Thill (Aug 28, 2021)

neuroanatomist said:


> One could also check reviews of the EF version, since they’re essentially the same lens.


Yeah same optics, I do like the option not having to use the RF to EF adaptor while using a TC with the "new" RF versions. Not sure that is enough to ignore the savings of picking up the EF version tho. 

I used the EF 400 F2.8 III via CPS test drive a few weeks ago and I am sold.


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## Nemorino (Aug 28, 2021)

neuroanatomist said:


> since they’re essentially the same lens.


"Just" the optics. The AF drive and the electronics are different. It would be interesting to compare both lenses if the performance is improved.

And I wonder what 


> Der duale Fokusantrieb sorgt mit kompatiblen Kameras für einen schnelleren Autofokus.


means. 
(The dual AF drive gives you faster AF with compatible cameras)
Quoted the German homepage of Canon.
There is nothing similar on the page of the EF 400 2.8.


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## koenkooi (Aug 29, 2021)

Nemorino said:


> "Just" the optics. The AF drive and the electronics are different. It would be interesting to compare both lenses if the performance is improved.
> 
> And I wonder what
> 
> ...


I suspect it's the same "Dual nano-USM" Canon is putting in other RF L lenses.


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## neuroanatomist (Aug 29, 2021)

Nemorino said:


> "Just" the optics. The AF drive and the electronics are different. It would be interesting to compare both lenses if the performance is improved.
> 
> And I wonder what
> 
> ...


‘Compatible cameras’ may mean those with high voltage batteries like the R3. That’s true for EF supertele lenses, as well.


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## Nemorino (Aug 29, 2021)

Yes, maybe. But a test would be nice if there is a difference. As mentioned before there is no such claim on the EF 400 page. So either the RF mount makes a faster AF drive possible ...
..or only the marketing changed.

Or have I justed missed a offical statement the AF being faster with a 1 series body?


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## Nemorino (Aug 29, 2021)

koenkooi said:


> I suspect it's the same "Dual nano-USM" Canon is putting in other RF L lenses.


No, two ring USM:


> Der Fokusantrieb mit zwei Ring-USM-Motoren


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## neuroanatomist (Aug 29, 2021)

Nemorino said:


> Or have I justed missed a offical statement the AF being faster with a 1 series body?


Not an ‘official statement’ per se, but mentioned on a few occasions by Chuck Westfall (Canon USA’s technical mouthpiece, sadly now deceased). For example, “In addition, the EOS-1D X achieves a higher lens motor drive speed with select L-series USM telephoto lenses than the 5D Mark III because of the 1D X’s more powerful battery pack.” (link) In other statements, he specified he is referring to EF supertele lenses.


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## Nemorino (Aug 29, 2021)

Thank for sharing this link!
I wonder why this benefit has not been mentioned on the homepage. I just had a short look on the specs of the 1d X III, nothing.


Back to the lens: I wonder how the AF performance of the two 400 could be measured by serious reviewers. Difficult.


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