Celts88 said:

The RF 600 f/4 would be the ideal lens for bird photography but it's super expensive and out of my price range (it's USD$14k here in Australia). I appreciate the EF 600 f/4 mkIII is essentially the same lense with built in adaptor but don't see any of the mkIII here in Oz, only mkII.

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According to CIPA, the RF version has a tad better IS, but in real life it shouldn't make any noticeable difference. I have the EF 600mm f/4.0 III, and I love this lens, its IS is quite impressive. Btw the mk II lens, which still was based on the conventional tele lens design with many big lens elements on the lens' front, is said to be a bit sharper. But it is heavier and on top more front heavy than the mk III lens, so shooting it hand-held is harder.

Celts88 said:

I don't see any issue with fogging but I live in Perth Australia and we very seldom have humidity here, unlike up North or over East. I've got an R1 so dim light doesn't affect me the same way with your R6

The RF 200-800mm is a fantastic lens for the price and I'd highly recommend it, as long as you appreciate it won't have the same pin sharpness or butter smooth Bokeh of the big white primes but you wouldn't expect that from a USD$2k lens. It's so easy to hand carry all day, and being able to go from 200mm to 800mm in a couple of turns is super useful.

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I have an RF 200-800, too, for occasions when I want a lighter lens and the flexibility of such a zoom. It is a real fun lens and sharper @ 800mm than I expected, but of course my 600mm prime is much sharper, even with 1.4x TC my EF 600mm f/4.0 III delivers noticeably sharper images @ 840mm. That said, in real life photography, what is more important than lab tests, the 200-800 performs very well, much better than its specs promise. There is only one drawback: from comments I learned that obviously lenses with different quality are out in the wild - I was lucky to get a really good copy that is quite sharp @ 800mm.

Celts88 said:

Primes are fantastic for what they do, but the zooms are so versatile in giving more options within the one lens. It's getting to the stage that the new zooms are only just a fraction less in image quality and if not a professional and making money from your shots then are the way to go, in my opinion.

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One advantage of zooms is when you shoot birds in flight, you can catch it using a shorter focal length and then zoom to longer focal lenghts. With a about 800mm prime it is a real challenge to find the bird in the viewfinder.

If I remember correctly, when Canon first came out with the RF mount, these was something strange with the image on third party lens. Unexpectedly strong vignetting and purple hue. I believe it has something to do with canon sensor technology and mirrorless cameras having much shorter distance between rear element and sensor. So light rays hit the sensor at much sharper angle, compared to dslr. Sony didn’t have that issue. It is possible canon mount requires different lens design in certain focal lengths for adequate performance. This is not worth it for a third party lens manufacturer to do. Maybe crop doesn’t have the same issue.

neuroanatomist said:

A camera body will show F00 and manual focus (MF) when it cannot communicate with a lens, which could be because there is no lens attached, because the lens is fully manual, or because there's a problem with the lens itself.

I went out birding over the weekend, mounted my usual combination of 600/4 II, 1.4xIII and the vanilla EF-EOS R Mount Adapter to my R1 and headed out. When I turned on the camera, it showed F00 and MF. I thought, "Oh, sh!t," and swapped on the 2xIII. That worked...but then it also changed to F00 and MF. So I mounted just the bare lens...and that was perfectly fine so I spent the day shooting like that.

When I got home, I cleaned all the contacts and tested various combinations again, including changing out the vanilla mount adapter for the drop-in version and my 3rd party adapter modified for an RF extender to fit behind it.

The upshot was this, and the situation is seemingly stable (through many trials over a couple of days, no changes). Happens on both the R1 and the R8, and with all three of the mount adapters.

• Bare 600/4 II – functions normally
• 600/4 II + 1.4xIII – F00 and MF
• 600/4 II + 2xIII – varies between:
  • Normal function
  • Showing an aperture value that can be adjusted, but still only MF
  • F00 and MF
  • The variation is caused by physical manipulation – twisting the lens in the mount or moving the lens, e.g., lifting it from pointing down into shooting position, affects the functionality
• 600/4 II + RF 1.4x (with Commlite adapter) – functions normally

The fact that I see this behavior with two bodies and three adapters suggests the problem is the TCs or the lens.

I haven't used the 2xIII TC quite some time, not since Comet C:2023 A3 Tsuchinshan-ATLAS in October 2024. So maybe the 2xIII failed sometime over the past 18 months (while sitting mostly undisturbed in a Pelican case with a dehumidifier unit), and the 1.4xIII failed sometime in the past 3.5 weeks since I last used it.

If it's the lens and not the TCs, the problem is specific to use with EF TCs and yet the problem exhibits different symptoms with the two TCs, and I don't know why that would be the case. Admittedly, I would prefer it to not be the lens, because the service life for the 600/4 II ended last year, so sending it to Canon is not an option. I could replace it with the RF 600/4, but I suspect we'll see a version of that lens with the 1.4x TC and hopefully fairly soon. I would love to have the latter and would not love buying twice.

One other idea occurred to me, literally as I was typing this post. I started to write that I don't have any other TC-compatible EF lenses with which to test the extenders...and realized that while that is true, I do have three other EF mount lenses that are physically compatible with the extenders, but don't report them to the camera body (TS-E 17, TS-E 24 and MP-E 65). So I tried the 1.4xIII and the 2xIII with the TS-E 24, and I found that the 1.4xIII shows F00, and the 2xIII shows an aperture value that can be adjusted.

It seems rather unlikely that both TCs independently failed, but I am thinking that's exactly what has happened. Sort of a Sherlock Holmes, "When you have eliminated the impossible, whatever remains, however improbable, must be the truth," sort of thing.

From a practical standpoint, assuming that I'm correct and both extenders have failed, I see no need to replace the 2xIII. One option would be to replace the 1.4xIII ($480 new or $280 used), but I can also just use the RF 1.4x behind my modified Commlite mount adapter, and just remember that I'm doing that since it's not reported in the EXIF. The downside to the latter is that I would not benefit from the DxO lens profile for the combo (though I could batch edit the EXIF and I suspect that DxO would use the 600 II + EF 1.4xIII profile, it still won't be the right profile).

Thoughts, suggestions, and sharing prior experience welcome!

Edit: the RF 1.4x itself does show up in the EXIF, but the exposure information doesn't reflect it, remaining 600mm f/4.
View attachment 228668

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I do not own a 600mm lens but recently traveled to South Africa in July 2025 and used the RF 100-300mm 2.8 (CPS trial run) lens. I mounted it with the RF 1.4x on my R1 and the RF 70-200mm 2.8 Z on my R52.

On the second day of shooting, I started experiencing multiple errors, including Err60, Err70, Err 80, and FOO. The R1 would give me an error, shut down, and wouldn’t turn back on. Of course, this happened during a cheetah kill! I swapped cameras to the R52, hoping the contacts on the R1 needed cleaning.

I returned to camp, cleaned the contacts on the R1 and 1.4x, and went out the next day. Unfortunately, the same errors occurred. This time, I also swapped cameras, but this time, I also got errors on the R52.

I contacted Canon South Africa, but since they couldn’t see the lens, they couldn’t really help me. However, they did mention that a new firmware was coming next week that might potentially fix the problem.

Interestingly, when I mounted just the bare lens (100-300 2.8), no errors occurred on either the R1 or R52.

When I returned to Canada, I sent my R1, R52, 1.4x, and their 100-300mm 2.8 to Canon Canada. Their findings were that, since they couldn’t replicate the errors I was getting, it had to be the 1.4x.

The fact that I have no problems with the 1.4x, I still believe the problem was with the 100-300mm 2.8. As I don’t own this lens, I cannot do any further testing.

Hope you get this sorted out!

AlanF said:

The R5ii has the reputation of having the fastest AF to lock on to a target of the A1ii/Z9/Z8 class. I saw this myself recently:

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It is fast, no question, but as I said the difference isn't noticeably big when we shot w/o TC side by side. But with TC, the difference is massive. Well, the Z8 is an older model, and Nikon struggled with the AF system in their first Z cameras anyway.

AlanF said:

So, maybe the difference in inherent camera AF is the answer, so you have more control experiments to do.

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We'll do

AlanF said:

By the way, Canon has produced a tele zoom with a DO optic, the EF 70-300mm f/4.5-5.6 DO IS USM in 2004.

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Ah, thanks, I missed that one.

neuroanatomist said:

One thing that would set it apart is the ability to extend the focal length further with TCs. For the target audience, that may be sufficient.

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that's true, I agree

neuroanatomist said:

Consider the Canon 600/4L IS that went from 5.4 kg (MkI) to 3.9 kg (MkII) to 3.1 kg (MkIII, RF) without DO. The 600/4 DO prototype from 2015 (between II and III) was much shorter but reportedly just under 3 kg.

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I know, Canon revolutionized the common tele lens design with the EF 600/4 III by moving main parts of the front lens elements (for corrections) back to the middle of the lens, what allowed for much smaller and lighter lens elements (and a much better balance). Sony and Nikon copied that idea with their latest 600/4 lenses, of course in a way they could work around Canon's patents. Nikon upped it by adding a built-in 1.4x TC, what made their Z 600/4 a bit heavier - but this is a smart move, no question, like Canon did it when they brought out their EF 200-400/4 zoom.

neuroanatomist said:

The supertele lenses all used to have a meniscus lens in front (essentially a flat piece of glass to protect the first refractive element, a permanent clear front filter). Dropping those from the design was a significant part of the weight saving for both Canon and Nikon lenses.

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Yepp, my old battered EF 500/4.5 still has one.

neuroanatomist said:

So, a 300-600/5.6 DO would probably weigh in somewhere close to the existing 100-300/2.8, but could be shorter. Personally, though a conventional 300-600/5.6 would not really interest me, a DO version that was shorter than my 100-300/2.8 (or even the same length) would tempt me.

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Well, I guess we'll have to wait and see with what Canon comes up (if), but it is always fun to speculate with all of you here in these threads.

Canon's ways of limiting Sigma are many and complex, not least because the intellectual property levers they have operate differently in different countries. In the US, reverse-engineering a standard is usually fine. In other countries it is sometimes not. One of the things that some of the Chinese vendors got into trouble over was claiming "RF Mount" branding on their packaging. Viltrox and Samyang may have had more trouble with the copyright/trademark (different mechanism) problem than with the an engineering/mount/patent issue. In the past, we've heard narrowly-stated comments from European Canon heads that turned out to be technically true, but not the whole truth. I recall a German executive talking about this issue back in the early RF days, and everyone got needlessly excited.

Then there's the business relationship issue. Most OEM camera companies use Tamron and Sigma to provide elements of lenses, or even whole lenses. Those OEM relationships are quite important to the companies, and it's not surprising that the little firms like Viltrox were the ones making RF lense while the ones with OEM contracts aren't.

Sigma's CEO has spoken around the issue in several interviews, most notably the recent one where the Petapixel crew visited him in Japan. My impression was that he wasn't able to speak because of an active provision that prevented him from speaking. He's a stand-up guy, and I'd put more faith in what he says (or indicates he can't say) versus a whole sack of OEM company executives.

Canon Rumors said:

I didn't notice what day it was.


Thanks. I left out the word dedicated. I didn't touch on the rest of it because none of that is hard. I think it all has more to do with Sigma not being able to manufacture to the scale required. People grossly overestimate how many lenses SIgma sells.

We now know that it has nothing to do with Canon. There will still be the naysayers, but it doesn't matter what you tell some people.. the vacuum can be strong.

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I disagree with your conclusion. Sigma already makes FF lenses that could be ported to RF. They have a mount conversion service costing about $250. I wanted them to convert two APS-C EF-M lenses to RF. They replaced the two lenses that I sent them with brand new RF lenses. They said they had RF M-mount lenses but hadn't received the conversion kits from Japan. As I recall, I got the new lenses on the days that the RF mount version became available in the U.S.

Does anybody doubt that Sigma would be overjoyed if the demand for existing FF lenses (plus a few parts) suddenly increased by, wild guess, 30%? They already know how to make lenses for the RF mount. They do it every day.

neuroanatomist said:

Well, it would put the ‘fluorine’ (fluorocarbon) coating to the test.

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When I visited the Isle of May with a small group of photographers, a tern shat on the front of the lens and the inside of the lenshood of one of the groups members. He had a hard time cleaning the lens and the black velvet of the lenshood. It was a Nikon, the terns did not dare shizzle on a Canon.

AlanF said:

This is a BIS - Red Kite (R5ii + RF 200-800mm).

View attachment 228692

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A red kite or a red shi*e?

Makes sense. I agree, it’s not the contract (license) that’s the issue here but some other business constraint. I was thinking more in terms of limited lens types (doesn’t exclude them from offering a lens, just not all possibilities) but manufacturing capacity is a real consideration.

Still, if just capacity then at worst case just add a control ring and the basic EF instruction set and call it a day for gen 1 so that the issue is more a lens mount swap like prior; go fancy for gen 2. People try too hard sometimes with all at once offerings.

All of Sigma’s current RF APS-C lenses DO have control rings: for the older ones it doubles up as the manual focus ring (same as all of Canon’s RF-S lenses) and the two newest primes and 17-40 have a separate control ring (which is used as an aperture ring on E and X mount versions). They also work with the in-camera focus scale, digital corrections, full time electronic manual focus options, and more. Older EF lenses don’t work well with IBIS either, so I don’t buy this idea that Sigma and other third parties are having to reverse engineer the RF mount.

None of the Sigma RF lenses offer autofocusing for the entire viewfinder however; anyone know if the other mount also suffer from this limitation?

Canon has stated in an interview in a Japanese newspaper that camera prices may be affected by rising prices of memory chips.

Google translated link to DCLife

P-visie said:

I hope it missed you (and your camera and lens) .

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Well, it would put the ‘fluorine’ (fluorocarbon) coating to the test.

neuroanatomist said:

Regardless, the 300-600mm might or might not come. It might be f/5.6, it might be f/4-5.6. There was going to be a 200-500mm f/4, with prototypes in the wild and rumored announcement dates. But then...there wasn't, and instead it was going to be a 300-600mm. In 2025. But then there wasn't. And now...in 2026.

I hope there is a 300-600/5.6, and your statement that you want something 'that's a bit more affordable than the current RF 600 f/4' may be reasonable as such a lens will likely be priced in between the 100-300/2.8 at $10.5K (USD) and the 600/4 at $14.5K. So if 'a bit more affordable' to you means a couple of thousand dollars cheaper, well and good. If you're hoping for a 300-600/5.6 costing <$10K USD, I suspect you're headed for disappointment even if the lens does get launched.

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I'd say I'm definitely hoping for something more like $8k, and I'm fully prepared to be disappointed lol. The 100-300 f/2.8 L definitely doesn't have me optimistic on the price being below $10k, so I think you're justified in your estimate.

I don't know what the market sensitivity is to ~8k vs. ~11k for the price (in USD), but I'm definitely sensitive to that (and seemingly, others here are as well).

I hope they release some compelling long options this year. The 14mm VCM and fisheye lens were just not in my interests at all, and I have the RF 50mm f/1.2, so the 45mm wasn't for me. A longer/high-magnification macro lens capable of taking extenders would be of interest. I definitely have a bit of GAS, but need Canon to put out something compelling (and uhh... hopefully more affordable than $11k).

AlanF said:

This is a BIS - Red Kite (R5ii + RF 200-800mm).

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I hope it missed you (and your camera and lens) .

P-visie said:

You stated (or I interpreted it that way) in another thread that the problem was solved by cleaning the contacts. Is that correct?

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Nope, I believe I stated that it didn’t solve my problem (or at least, that’s what I meant to state). That was before I deleted all of that, subsequent to your post identifying the real problem of the camera in that thread being a 6D.

You stated (or I interpreted it that way) in another thread that the problem was solved by cleaning the contacts. Is that correct?

In terms of third party lenses, I found over the years the following:

• Optical quality tended to be equivalent to the better non-L Canon lenses. For example, the gold ring USM lenses. Eventually Sigma really stepped up its game and produced lenses that specifically solved Canon flaws (UWA coma, for example) and/or generally competed with mid-tier L quality (24-105L, for example). I have over time used (and sometimes owned) lenses from Sigma, Tamron, Tokina, and IRIX (non-cinema).
• Third party compatibility has greatly varied over time, an issue which continues through today. The USB docks helped, but never assured a guarantee. It really made the investment of cash into more expensive third party lenses ($1k+, let alone $6k+) a questionable investment over a decade. In the latest example, something in cameras after the R6 / R5 broke IRIX compatibility — and all that lens series does is confirm focus plus transmit metadata (e.g., lens type). USB firmware docks on the Canon side are largely discontinued, and so with that an inevitability of camera compatibility breakage.
• In the modern context, quality third party lenses tend to be priced similarly EF lenses anyhow. A solid Sigma costs the same as a solid EF comparable, and either one will have tradeoffs in optical quality, DLO integration, or lens barrel robustness.
• Very few compete optically or in lens body construction with modern L RF designs.

I've yet to encounter any third part lens that competes with premium contemporary Canon lenses, and I've yet to have a friend say they have either. If someone is willing to spend $10k in any currency on a single lens I sincerely doubt the lack of third party lenses are going to cause said person to jump ship because of a missing third party line — or it's a rare, very niche situation. Canon makes a premium product that is as expensive as "L" because it caters first to professionals.

In an older IT company I worked at when getting going in the industry the president used to tell us that we had one flagship product for a market and all other products just needed to be technically eligible — that is, tick enough boxes on paper to be allowed to compete for client funds but by no means had to be better than anyone else's (or even half as good). Canon's non-premium tier probably meets the "technically eligible" definition in a modern context of other manufactures. For example, the STM non-L lenses get the job of focusing photons onto a sensor done and they're fine for what they are but they're not the reason for someone to start with Canon cameras as opposed to Sony or Nikon; rather, they make a Canon camera body equally eligible for a newcomer's cash.

I think from Canon's perspective the EF catalog, which is still present for common use cases, is a de-facto third party lens option for the RF mount. Want to save money? Sigma has a 12-24 f/4 but Canon EF has an 11-24 — align sales and they're the same effective price in Canada. Sigma has a 24-105 f/4 but Canon has an EF 24-105L II IS USM — align sales and they're the same effective price in Canada. Ditto for Tamron, and ditto for IRIX (but in IRIX's case Canon also has AF). Might some of these be optically better than EF? Sure, but there's also no assurance they'll work on the R1 II, or the R5 III — but the EF lenses will.

All of my third party lenses have been sold off, and they were all sold off for compatibility reasons. I won't buy more until they are officially supported by Canon. Not while EF exists new or like-new with warranty, at any rate.

That stated, I think the people in this forum buying $10k+ lenses need to keep in mind that many people want the experience of exotic lengths but cannot justify the lofty price of new editions. And for mediocre non-L products (not bad, just average for the industry all factors averaged out) then why not cheaper third party options? Not everything is brute force making money or having the most Instagram followers— it might be nostolgia for 1990s photography (enter Sigma's more affordable Great White or prior Great Blacks). B+ and A- for 2/3rds the cost for most people will be perfectly fine — they probably aren't editing anything so refined that A+ would make the difference anyhow.

Myself, I probably represent an aspect of this category. I am well heeled thanks decades of hard work and good fortune, but I don't buy the $10k lenses. Why? I have a farm and animals are expensive; I am an enthusiastic power lifter who spent loads of money building a sweet home gym; I like to travel; etc. Eventually I want to retire. My wife has her priorities. A- for me is good enough as a (generally) non-commercial photographer, and if Sigma offered select lenses under Canon blessing then I'd think about them in a serious way. Jump ship without? Obviously not. Consider them as alternatives to B through A- RF lenses? Sure thing.

For people much less fortunate (industry specifics, now retired, many mouths to feed, injury with medical needs in an expensive health system, etc.) these options actually might make the selection of a platform a real material matter. This being a Canon forum, I don't think it's good enough to say just go buy Sony or Nikon — obviously that's an option — but the nature of this forum is hope for the future for the Canon community. I think that just like in the EF era third party options form entry points, retirement enjoyment, etc. I don't think people should sneer as hard as they do at the possibility. Just because many of us are fortunate enough to have all Canon gear doesn't mean that's the only valid path forward. And even those of us with non-Canon gear (some of my gear is solid but not Canon) we'd like to replace them with non-$10k but better than meh options that are Canon-compliant, and if a third party makes that a better likelihood then hurray. I mean, $4.1k for a 500mm f/5.6 with weather sealing from Sigma (or their $7.7k f/4 EF mount edition still in stock) vs $11.5k for a Canon EF 500 f/4 for your average non-commercial photographer? Only an ignorant person would tell the candidate to avoid the Sigma and cough up an extra $7.4k for... what? I can't think of the reason.

This is a BIS - Red Kite (R5ii + RF 200-800mm).

IMO, Sigma is often first out of the gate. Then, some time later, Canon comes along and releases something that is typically better, but also more expensive.

Examples.
14 mm f/1.4 - the ultimate astro lens. Sigma's version came out in 2023, Canon's version came out recently.
100-300 f/2.8. Sigma's 120-300 f/2.8 OS HSM came out in 2010.

Ditto for Tamron. Their 28-75/2.8 was released in 2021 and sold very well. People liked its speed and compact design. Canon released its copycat 28-70/2.8 in 2024.

dolina said:

Sigma offers attractive Art lenses at select focal lengths but the assertion that they could motivate system-switching ignores optical benchmarks, autofocus performance, ecosystem depth and system integration. Canon RF is superior in coverage, optical quality, AF speed, system cohesion and future-proofing.

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I am not sure I understand to what the RF mount is superior... other mounts have pros and cons and their own areas of excellence, same as RF does

And I fail to see how opening RF to 3rd party FF AF lenses would not improve the mount's coverage and depth? After all Sigma is offering a number of lenses that have currently no equivalent in RF.

mangobutter said:

Shucks, so no AF at ALL when using the 1.4x III.

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You can AF with the combination in Live View. It’s slow, but it works. Live view works at f/11 with the 2x TC as well.

Interesting. I sort of thought it had to do something with that but i thought i'd at least be able to use central point. Shucks, so no AF at ALL when using the 1.4x III. Good to know nothing wrong with my 6D. Thanks

m4ndr4ke said:

While I'm pleased with the way the RF system has been developing, I have to recognise that third-parties could always add something, and it's not just low end products.

There are now some nice lenses available for RF, but third-parties have other very competitive offers as well, being Sigma, in my opinion, the biggest "threat".

Lenses like theirs 35mm f/1.4 and f/1.2, 50mm f/1.4 and f/1.2, 28-45mm f/1.8, 28-105mm f/2.8, and now the 200mm f/2 and 300-600mm f/4, plus their Contemporary primes, for instance.

It may be your understanding that Canon offers a few lenses that are somewhat similar to these Sigma offerings, and I get that, but the thing is: some of these cost half the price of Canon's.

Is the RF 24-105mm f/2.8 twice as good as the Sigma 28-105mm f/2.8? Debatable.
Is the RF 28-70mm f/2 twice as good as the Sigma 28-45mm f/1.8? Again, debatable.
Is the RF 50mm f/1.2 twice as good as the Sigma 50mm f/1.2? Same.
Lower end 20mm? We have none.

And a lot of their lenses (most) are very robust, weather sealed (all?) and feature linear motors and internal focusing mechanisms.

Don't be mistaken, the pressure is high for Canon, as these other lens manufacturers are showing off their value daily with other lens mounts, and Sigma is doing potentially enough to motivate changing systems for many photographers.

Also, keep in mind: Sigma is a third-party manufacturer in relation to Canon, Sony, Fuji and Nikon's systems, but they are a primary manufacturer for their own cameras and the L mount. Plus all the other brands.

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Sigma offers attractive Art lenses at select focal lengths but the assertion that they could motivate system-switching ignores optical benchmarks, autofocus performance, ecosystem depth and system integration. Canon RF is superior in coverage, optical quality, AF speed, system cohesion and future-proofing.

According to this table on shuttermuse, the 6D AF does not work with f8 (EF 100-400mm II f5.6 + 1.4 extender = f8).