EF Lenses Focusing Issues with Adaptor and EOS R3

[SCHOON73]

Is anyone using a 300mm 2.8 EF or 400mm 2.8 EF lens with adaptor and R3 or R5 mirrorless camera? Wondering if there are focusing issues associated with using the adaptor?

[Peter]

R6 and 300/2.8L IS USM work without AF issues, but focus preset doesn't work.

[SCHOON73]

Thanks for the info. I'm looking to purchase a used EF 300mm 2.8 or 400mm 2.8  lens for sports photography as a more affordable option to an RF lens to use with my r3 and r5 cameras.  I don't generally use focus preset, so it's not a deal breaker!

[jrprochaska]

I don't have either of those cameras or lenses.  But there may be a problem with Canon mirrorless cameras with longer EF lenses.  You might check my earlier post today "Canon EOS R7 Blurry Images".

[SCHOON73]

Will do! 

[deebatman316]

Are you talking about the original non-IS EF 300mm F/2.8L USM lens (released in 1987 which was the very first USM lens from Canon) Then the original non-IS EF 400mm F/2.8L USM lens (released in 1991). Or the newer IS counterparts that replaced these lenses.

-Demetrius

Current Gear: EOS 5D Mark IV, EF 16-35mm F/2.8L III USM, EF 24-70mm F/2.8L II USM, EF 50 F/1.8 STM, EF 85mm F/1.8 USM, EF 70-200mm F/2.8L IS III USM, 470EX-AI & 600EX II-RT

Retired Gear: EOS 40D & Sigma 17-50mm F/2.8 EX DC OS HSM

[SCHOON73]

The newer IS counterparts

[deebatman316]

The lenses should work and perform fine as if they're on an EF Mount camera. Even when there being adapted to an RF Mount body via the EF-RF Mount adapter. I've only briefly used the original EF 300mm F/2.8L USM (non-IS version). This lens has focus by wire manual focus. All of Canon's early prime telephoto and super telephoto lenses were this way.

-Demetrius

Current Gear: EOS 5D Mark IV, EF 16-35mm F/2.8L III USM, EF 24-70mm F/2.8L II USM, EF 50 F/1.8 STM, EF 85mm F/1.8 USM, EF 70-200mm F/2.8L IS III USM, 470EX-AI & 600EX II-RT

Retired Gear: EOS 40D & Sigma 17-50mm F/2.8 EX DC OS HSM

[SCHOON73]

Thanks for the info!