Should I buy ef lenses for my EOS R6 II?

[dikebki1]

Hi I was thinking about adding a 70-200 f2.8 to my inventory. The rf mount is very expensive so I thought about buying a used ef mount lens. Some friends of mine said they don’t see any loss of quality with the ef and a adapter, some say there is a lot of loss in quality. I was wondering if you could share your experience and if you have any advice? Thanks 🙂

[deebatman316]

I would not invest ANY EF lenses if you own an RF Mount camera. Unless there isn’t an RF Mount equivalent lens. Older EF lenses have limitations when adapted to RF Mount cameras. Such as the highly advanced AF system not being fully supported. Or 12 fps being available.

[March411]

deebatman316 makes a valid point. For me the question comes with a caveat or two. If you can't afford the RF version and the lenses you are thinking of purchasing are not reaching end of service it may make sense.

I have purchased and still own several EF lenses from both Canon and Sigma. Personally end of service is my biggest consideration. There are three different versions of the lens you inquired about, only the EF70-200 2.8L IS III USM should be a consideration.  

• EF70-200 2.8L USM: May 2026
• EF70-200 2.8L IS II USM: May 2025
• EF70-200 2.8L IS III USM: Undecided

When I asked myself the same questions as you I decided to dive deep, I did in this post I went out and did a fair amount of research. I left my findings in the Canon knowledge base, check out this link there is some decent information with links for reference: Canon (MILC) - Lenses - EF or RF 

Again deebatman316 point is valid, EF lenses are heavier and RF lenses have a 12-pin connection to the camera, while EF lenses have 8 pins. This allows RF lenses to communicate with the camera faster, more efficiently and offer more functionality. That being said, the EF lenses I maintain work far better on my MILC then my DSLR's, fast and overall better keeper rate but they are being mounted on a superior R body.

If you decide to go EF don't make the same mistake I did and try third party adapters, they are very inconsistent! New or used the simple Canon EF - RF adapter will greatly improve the performance of the lens.

[shadowsports]

The RF 70-200 f2.8 is a favorite of mine.  As my colleagues pointed out, investing in EF glass is a losing proposition in the longer run.  If you want the flexibility of being able to use an RF TC, then you'll need to buy the 24-105 Z internal zoom model.  I really like the compactness of the first gen 70-200 and don't mind that it's an external Zoom.  I also rarely use a TC so this is a non-issue for me.  The lens is extremely sharp and high performing.  It's exceptional for portraits and indoor venues with low light.  The EF model has these same attributes.  In the end, however, lenses are your real investment in photography.  Body's come and go.  Have you considered Canon refurbished?

https://www.usa.canon.com/shop/lenses/refurbished-lenses

[ebiggs1]

"...the highly advanced AF system not being fully supported. Or 12 fps being available."

If you feel, as a lot of people, you don't need or would use these features you will not miss them. Just because a camera can do something doesn't mean much if it isn't something you need. There are some features on my 1 series cameras I never have used.

I doubt you will be able to see a different in IQ unless perhaps you are a pixel peeper and then maybe not. Remember the lens you have is always better than the lens you wished you had.

[March411]

To ebiggs point there are several EF lenses that can't achieve the supported FPS but there are many that can if you are looking for that functionality. The EF70-200mm f/2.8L IS II USM and EF70-200mm f/2.8L IS III USM appear to be supported. Due to end of service the EF70-200mm f/2.8L IS III USM would be your best option.

EF Lenses supporting maximum continuous shooting speed
EF24mm f/2.8 IS USM	EF400mm f/2.8L IS II USM	EF24-105mm f/3.5-5.6 IS STM	EF200-400mm f/4L IS USM Extender 1.4x
EF28mm f/2.8 IS USM	EF400mm f/2.8L IS III USM	EF24-105mm f/4L IS II USM	EF-S24mm f/2.8 STM
EF35mm f/1.4L II USM	EF400mm f/4 DO IS II USM	EF24-70mm f/2.8L II USM	EF-S35mm f/2.8 Macro IS STM
EF35mm f/2 IS USM	EF500mm f/4L IS II USM	EF24-70mm f/4L IS USM	EF-S10-18mm f/4.5-5.6 IS STM
EF40mm f/2.8 STM	EF600mm f/4L IS II USM	EF70-200mm f/2.8L IS II USM	EF-S18-55mm f/3.5-5.6 IS STM
EF50mm f/1.8 STM	EF600mm f/4L IS III USM	EF70-200mm f/2.8L IS III USM	EF-S18-55mm f/4-5.6 IS STM
EF85mm f/1.4L IS USM	EF8-15mm f/4L Fisheye USM	EF70-200mm f/4L IS II USM	EF-S18-135mm f/3.5-5.6 IS USM
EF100mm f/2.8L Macro IS USM	EF11-24mm f/4L USM	EF70-300mm f/4-5.6 IS II USM	EF-S18-135mm f/3.5-5.6 IS STM
EF300mm f/2.8L IS II USM	EF16-35mm f/2.8L III USM	EF70-300mm f/4-5.6L IS USM	EF-S55-250mm f/4-5.6 IS STM
	EF16-35mm f/4L IS USM	EF100-400mm f/4.5-5.6L IS II USM
https://cam.start.canon/en/H001/supplement_0080.html