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R5 + Sigma 70-200 2.8 Sport + Canon 2x Mk III teleconverter


I have an R5 and a Sigma 70-200 2.8 Sport, I'm interested in the 2x III teleconverter for wildlife - mostly national parks and occasional birds. Nothing too challenging like birds flying towards the camera.

Does anyone use this specific combination and can comment on the image quality and autofocus performance? Image quality is my main concern.

Image quality: I know 2x teleconverters magnify any lens imperfections, but I have been very happy with the sharpness of the Sigma 70-200 even on extremely tight crops and pixel-peeping. I feel like I should not be too concerned about the effect of image quality when using the 2x III. I would be surprised if the quality of the glass in the teleconverter is poor, considering they are used on the large Canon primes.

Autofocus: Many people discuss how the 2x tele has slower AF on DSLRs compared to the 1.4x (5D and 7D mostly), but the R5 has a more powerful AF system that works very well in low light, so does the 2x tele still significantly slow down autofocus on the R5?

Is this a good combination? Easier to stomach this cost than buying a used EF 100-400mkII, and the 150-600 Sigma sport is way too heavy.



I don't think any of us regulars do.  You are only the second person I've heard from that owns the 70-200s lens.  None of us are big users of the 2.0x TC except for Rodger, Newton and maybe Trevor for the exact reasons you mentioned.  

In all honestly, the 70-200 is not the best lens for birds, even if they aren't flying.  No doubt the 70-200s is sharp.  I've owned several Sigma lenses (still do) and they are very good for the money.  

I hate to see you drop cash on an EF mount TC for your R5, and then you are going to EF to RF adapt it.  Would it work, probably.  Would I do it.  Probably not.  Others will assuredly have comments to share on this.  

Bay Area - CA

~R5 C ( ~RF Trinity, ~RF 100 Macro, ~RF 100~400, ~RF 100~500, +RF 1.4x TC, +Canon Control Ring, BG-R10

~DxO PhotoLab Elite ~DaVinci Resolve ~Windows11 Pro ~ImageClass MF644Cdw ~Pixel6 ~CarePaks Are Worth It


You will have to leave me out of the frequent user group of the 2X, even with the 300 f2.8 (which I believe is the sharpest of the great white primes) there is just too much degradation with a 2X.  The 300 or 400 with a 2X still produces very nice images that are better than what a lot of bare lens can generate BUT if you compare the sharpness and contrast of the bare lens or with the 1.4X to the 2X it just doesn't look good.

I just don't think the 2X is worth it unless you have a situation where you have to double the focal length and are willing to give up a lot of quality to get there.


EOS 1DX M3, 1DX M2, 1DX, 5DS R, M6 Mark II, 1D M2, EOS 650 (film), many lenses, XF400 video

Rick, I sold the EF 2X III several years before I picked up the R5 and R6. I bought it mainly out of curiosity and just didn't like the IQ hit using the 5D mark IV and EF 100-400L II. I also have the EF 1.4X III, which was/is manageable on that rig with proper light and some post but it didn't transfer, to my liking, on the R's. My plan was to adapt my EF glass, but that just didn't happen and I ended up going full on RF glass within a few months of getting the R5 and 6 (L RF trinity, RF 100L macro, RF 100-500L, and RF 100-400), I also bought the RF 1.4X mainly for my wife's RF 100-400 and the R6 and R6 mark II. The RF 1.4X does a good job on both the RF 100-500L and the RF 100-400, but as Waddizzle mentioned, not as sharp as the bare lens, particularly on the R5.

@ayush0962, you would probably get acceptable images with the Siggy and EF 2X, but you don't sound like someone that wants "acceptable". Also, it's not that the 2X has bad optics, it's that it adds more elements to the equation. You are correct about AF using the R5 so if you use the 2X, I just don't see that as a problem. You may loose some focus points around the edges, but judging from my experience with the 1.4X on the R5, AF is still snappy up to f/22. IMHO, having used 2X's, I wouldn't waste the time or money and Rodger's (wq9nsc) advice rings true as he probably has the best glass.

If at all possible, I would (and did) lay off of the EF glass. If you want more reach, I would suggest the RF 100-500L and if that's out of budget, the RF 100-400mm would only set you back a few hundred dollars more than the 2X extender. I own this lens (I think Rick "shadowsports" does as well) and although it lives on my wife's R6 mark II, I have used it on the R5 and it's a very nice lens, probably not as sharp as your Siggy, but I suspect better than Siggy w/2X extender. Just a thought 🙂



Thanks for adding your thoughts.

Bay Area - CA

~R5 C ( ~RF Trinity, ~RF 100 Macro, ~RF 100~400, ~RF 100~500, +RF 1.4x TC, +Canon Control Ring, BG-R10

~DxO PhotoLab Elite ~DaVinci Resolve ~Windows11 Pro ~ImageClass MF644Cdw ~Pixel6 ~CarePaks Are Worth It


You’re better off buying a longer lens.  There is no substitute for real focal length.

I think investing in a Canon 2x is not a good idea for a couple of reasons.  One, your image quality will suffer due to your AF system receiving significantly less light.  You just might get an error message from trying to use the Canon TC with a Sigma lens.

Lastly, if I owned an R5, then I would not invest in EF mount gear.  Unless, of course, someone wants to sell an EF 400mm f/2.8 II in mint condition for $400 USD.

"The right mouse button is your friend."

Last thing I'd add.  The RF 100-400 was on sale in the Canon refurb store for $399 yesterday...  Sadly its sold out now 🙁


But in stock at B&H new for $549.  Still a nice deal.  Don't let the f8 at 400mm scare you.  Its only noticeable when you have something solid directly behind you subject.  Otherwise, the background still melts away.  

Bay Area - CA

~R5 C ( ~RF Trinity, ~RF 100 Macro, ~RF 100~400, ~RF 100~500, +RF 1.4x TC, +Canon Control Ring, BG-R10

~DxO PhotoLab Elite ~DaVinci Resolve ~Windows11 Pro ~ImageClass MF644Cdw ~Pixel6 ~CarePaks Are Worth It

@shadowsports wrote:

"Don't let the f8 at 400mm scare you.  Its only noticeable when you have something solid directly behind you subject.  Otherwise, the background still melts away." 

Spot on! I don't know what Canon has done with these newer R's and the RF glass, but small apertures just work. I know it's hard for DSLR users to grasp, but f/7 and up isn't the problem it used to be. I posted some shots in the users photo section on this forum that my wife took with the R6 mark II and RF 100-400 that were at f/40 and ISO 10,000. Yes, she did that by mistake, but the images were very sharp with no noticeable noise. It's one of the sharpest budget lenses we have ever used and I like it's versatility and light weight. We shoot a lot of birds and have no trouble getting shots out to 100 feet or flowers and insects just a few feet away at 400mm.

These examples using the RF 100-400mm were taken with the R6 mark II, but IMO the R5's 45mp resolution would have brought out more detail.

R6 mark II and RF 100-400 at over 100 feet. The R5 would have allowed for a tighter crop of the hawk, but IMO the R6 II w/RF 100-400 did a good job. She shot this at f/16 so bokeh isn't that great.

Red-shouldered HawkRed-shouldered Hawk

R6 mark II and RF 100-400 from MFD, 3 or 4 feet, just not sure, but it was close in. This one is at f/10 so the bokeh is a bit better.

Pink Wood SorrelPink Wood Sorrel

R6 mark II and RF 100-400. This 1/2" long Robber Fly was shot from 5 or 6 feet at f/8, so the bokeh is just cream 🙂

Robber FlyRobber Fly



Your images are a testament.  

Bay Area - CA

~R5 C ( ~RF Trinity, ~RF 100 Macro, ~RF 100~400, ~RF 100~500, +RF 1.4x TC, +Canon Control Ring, BG-R10

~DxO PhotoLab Elite ~DaVinci Resolve ~Windows11 Pro ~ImageClass MF644Cdw ~Pixel6 ~CarePaks Are Worth It
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