# Canon EOS R5 + any RF 35 mm = terrible back focus



## Dmitri_Kahm (Oct 10, 2020)

Hi all!

I have encountered a following problem. Brand new R5 and brand new RF 35 with or without the newest firmware produce a terrible back focus for apertures above 1.8. At aperture 4.0 the back focus is the worst, resulting in the least acceptable resolution in the point of intended focus. I have also tried another copy of rf 35 and the problem persists. This problem sometimes vanishes by itself for no reason and the camera works well until shutdown. I have tried all kinds of settings to find out what might trigger it, firmware updates, all kinds of AF and modes- nothing helps. The only way I can achieve normal results is to mount a 50 mm 1.2 rf first ( flawless work) and then change it to 35 mm without turning off the camera. For some reason it will do a trick and a camera fill hit the focus at any aperture after that until shut down.

I attach a link with a couple of center crops of the target. They are both shot from a tripod at 1/1000 a second, AFS stabiliser off ( but nothing changes if it is on), aperture 4.0, iso 1600 ( yes ISO is high, no if you set it to 100 nothing changes), distance to a target is around 3 meters. One photo is taken after changing a lens from 50 mm, the other straight after I restarted a camera a moment later.

I also attach a center of a shot made at 1.8 aperture which is clearly sharper than the one made at 4.0 after the restart.

Why am I sure that is is a back focus? Because I ran several photoshoots and always saw focus on ears rather than on eyes. And because I tried gazillion shots on a ruler and I clearly see a problem.

What am I asking? I am asking the ones who have this combo to test it and see if the same thing happens. Just pick any target with small text on it like some package and shoot it in AV mode from a tripod or any steady surface at 1,8 and 4,0 apertures and watch if the resolution of the text downgrades.

What I am NOT asking for. Please do not advise to change my shooting technique or make any assumptions unless you do the test yourself. I made this test numerous times accompanied by a technician in a camera shop and I DO manage to achieve perfect results with other lenses or straight after changing the lens from 50 to 35 until I switch the camera off. I also tested another lens in another shop, same result. I already contacted an authorised Canon technician and will take the combo to him on Monday so you will have nicer pictures at 100 ISO, rulers etc.

I do know the Optical limits review, where they stated that 35 rf is prone to focus shift. The focus shift that they illustrated is incomparable to the one I get. Mine results in OOF images where at the sweet spot of the lens you get the worst results.

The crops form undedited raws are attached via the link

LINK REMOVED BY MOD_1 as we don't know the safety of the link.


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## Viggo (Oct 10, 2020)

Besides the fact that it works when mounting 50 first, my initial thought is that this is focusshift like the EF 50 L. Since the R5 focuses wide open it doesn’t matter if it’s mirrorless.


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## Mod_1 (Oct 10, 2020)

Dmitri_Kahm said:


> Hi all!
> 
> I have encountered a following problem. Brand new R5 and brand new RF 35 with or without the newest firmware produce a terrible back focus for apertures above 1.8. At aperture 4.0 the back focus is the worst, resulting in the least acceptable resolution in the point of intended focus. I have also tried another copy of rf 35 and the problem persists. This problem sometimes vanishes by itself for no reason and the camera works well until shutdown. I have tried all kinds of settings to find out what might trigger it, firmware updates, all kinds of AF and modes- nothing helps. The only way I can achieve normal results is to mount a 50 mm 1.2 rf first ( flawless work) and then change it to 35 mm without turning off the camera. For some reason it will do a trick and a camera fill hit the focus at any aperture after that until shut down.
> 
> ...



Please attach jpeg images. I deleted the link as you are a first time poster and we do not know the safety.


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## Mt Spokane Photography (Oct 10, 2020)

I've used the two quite a bit now. AF has been amazingly good, I don't recall getting even one out of focus shot. I'd tend to think there is a lens issue.


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## Dmitri_Kahm (Oct 10, 2020)

Mt Spokane Photography said:


> I've used the two quite a bit now. AF has been amazingly good, I don't recall getting even one out of focus shot. I'd tend to think there is a lens issue.


I highly doubt that it has anything to do with a lens. I tested the body with another copy, identical results. And I already said that I can make the combo work if I attach the lens after I unmount 50mm. 99% sure that the body brains are f**d up. Now wondering how I am going to explain that to canon. This all sounds as an absurd but here it is.


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## SHAMwow (Oct 10, 2020)

Yeah now that that AF is on board, if I have huge focus issues I'd assume its a lemon lens and return it. Depends how large the miss is though as they have been patching small focus issues through firmware. This doesn't sound like that though.


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## Dmitri_Kahm (Oct 11, 2020)

SHAMwow said:


> Yeah now that that AF is on board, if I have huge focus issues I'd assume its a lemon lens and return it. Depends how large the miss is though as they have been patching small focus issues through firmware. This doesn't sound like that though.


This is not most surely not a lemon lens, as I tested another brand new with similar results. And there is away to make a lens work, described in the original post: switching to it from the rf 50 mm 1.2 ( switching from zooms does not help). This looks like some crazy bug on the board.


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## SHAMwow (Oct 11, 2020)

Dmitri_Kahm said:


> This is not most surely not a lemon lens, as I tested another brand new with similar results. And there is away to make a lens work, described in the original post: switching to it from the rf 50 mm 1.2 ( switching from zooms does not help). This looks like some crazy bug on the board.



Okay then. Based on this and the OP, I"m not sure what the goal of posting about this was. I'm glad you found a work around, but that is incredibly random and arbitrary. Good luck with the issue though.


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## YuengLinger (Oct 11, 2020)

Unless I missed it, please let us do some simple trouble-shooting:

Does the R5 in question work with other lenses without the same problem?

Does the 35mm in question work on another Rf-mount body without the same problem?

Please be clear. Thank you!

ALSO: Your "flat" charts aren't helping a lot. We need to see a shot of a target that is at a 45 degree angle to the plane of the sensor, so that the far end, the target point, and the close end are not all in the same plane of focus. Like the one shown right at the top of the article here:









AF Microadjustment Tips


AF Microadjustment Tips




www.the-digital-picture.com


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## Wagerd (Jan 25, 2021)

Dmitri_Kahm said:


> Hi all!
> 
> I have encountered a following problem. Brand new R5 and brand new RF 35 with or without the newest firmware produce a terrible back focus for apertures above 1.8. At aperture 4.0 the back focus is the worst, resulting in the least acceptable resolution in the point of intended focus. I have also tried another copy of rf 35 and the problem persists. This problem sometimes vanishes by itself for no reason and the camera works well until shutdown. I have tried all kinds of settings to find out what might trigger it, firmware updates, all kinds of AF and modes- nothing helps. The only way I can achieve normal results is to mount a 50 mm 1.2 rf first ( flawless work) and then change it to 35 mm without turning off the camera. For some reason it will do a trick and a camera fill hit the focus at any aperture after that until shut down.
> 
> ...


I just found this thread because I was having the same issue with the R5 and my 70-200 2.8 EF is L. Focus point is highlighted on the eye of a squirrel, but the real focus was an inch behind him in the grass. Same results repeatable. RF lenses don’t seem to have the same issue.


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## YuengLinger (Jan 25, 2021)

Wagerd said:


> I just found this thread because I was having the same issue with the R5 and my 70-200 2.8 EF is L. Focus point is highlighted on the eye of a squirrel, but the real focus was an inch behind him in the grass. Same results repeatable. RF lenses don’t seem to have the same issue.


This does not seem to be "the same issue." OP, who has NEVER FOLLOWED UP, was using an RF prime lens, not an EF zoom lens.

As this thread, in my opinion, should die a natural death unless the OP or somebody who does have the OP's same problem posts, I would suggest you start a new thread. Just a suggestion. Then you might find others with similar problems, and suggestions.

That said, I would like to be helpful. Have you had similar problems with your EF 70-200mm lens on an EF body? Did it, by any chance, need extreme AFMA--close to a max value? Have you tried it on any other Rf body? 

Finally, while a squirrel might be sitting still and seem a good sample target to test the combo, have you tried using a lens target with an angled ruler under carefully controlled conditions?


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## Dmitri_Kahm (Jan 25, 2021)

YuengLinger said:


> This does not seem to be "the same issue." OP, who has NEVER FOLLOWED UP, was using an RF prime lens, not an EF zoom lens.
> 
> As this thread, in my opinion, should die a natural death unless the OP or somebody who does have the OP's same problem posts, I would suggest you start a new thread. Just a suggestion. Then you might find others with similar problems, and suggestions.
> 
> ...



Hello! here is the OP! And if I offended you bu not replying I am sorry for that. After all I tried several 35mm RF's and they were all back focusing on my R5 at smaller appertures. There was no way for me to test another R5 at that time. However, both EF 35 2.0 and EF 35 1,4 were focusing perfectly, no issued with small apertures. So I bought EF 35 2.0 and never experienced this problem again. 

As for the problem of Wagerd, I am actually experiencing a similar problem with backfocus of RF 70-200 right now and there is a much better documented thread for that here https://www.canonrumors.com/forum/t...70-200-rf-ef-2-3-and-canon-r5-in-servo.39990/

Hope that might be useful


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## YuengLinger (Jan 25, 2021)

Please note that this same OP is apparently posting variations of this thread in other forums, but he uses different cameras and lenses to start the same topic.

For example, read through this DPR thread, which is going to be familiar except for the lens, and where another poster asks if he ever resolved similar issues with a Nikon body he was complaining about. 

R5 and any 70-200 (RF/EF) results in awful backfocus in SERVO: Canon EOS R Talk Forum: Digital Photography Review (dpreview.com)

What in the world?


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## Dmitri_Kahm (Jan 26, 2021)

YuengLinger said:


> Please note that this same OP is apparently posting variations of this thread in other forums, but he uses different cameras and lenses to start the same topic.
> 
> For example, read through this DPR thread, which is going to be familiar except for the lens, and where another poster asks if he ever resolved similar issues with a Nikon body he was complaining about.
> 
> ...


Do you imply that I am simply fooling everyone around?
The post on DPP is absolutely about the same Canon r5 I am posting here. I provided the same pictures.
What kind of evidence you need to persuade you the I am not kidding? Mope pics?
The Nikon D850 + 24-70 OOF for side points is after all a known issue.


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## YuengLinger (Jan 26, 2021)

Dmitri_Kahm said:


> Do you imply that I am simply fooling everyone around?
> The post on DPP is absolutely about the same Canon r5 I am posting here. I provided the same pictures.
> What kind of evidence you need to persuade you the I am not kidding? Mope pics?
> The Nikon D850 + 24-70 OOF for side points is after all a known issue.


I'm am explicitly stating that your pattern of similar posts about different combinations of lenses and bodies is odd.


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## Mt Spokane Photography (Jan 27, 2021)

I had my RF 35mm on my R5 here on my desk and tried taking a photo of a 45 degree slanted ruler with a black sharpie mark at the apparent point of focus. I used magnification of the lcd to place the mark in the center of the AF box. 

My first photo was at f/16, and as expected the entire ruler was in sharp focus at about 2.5 ft more or less. I did not bother to show it.

So, I changed to f/2 so the effects of front or rear AF became obvious. I took 2 more images the same way, then backed off to about 5 feet and took one more. Its the bottom image.

As expected, the first image below had the center of the image in sharp focus. The image taken from twice the distance showed more of the image to the rear in sharp focus than in front.

That's what is expected. As distance is increased, the depth of field behind the center of focus increases dramatically. You can see that in the DOF calculator at the bottom. Is the distance grows, the area behind the focus point gets more dof.That does not mean the camera is back focusing, its just the laws of optics.


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## Dmitri_Kahm (Jan 27, 2021)

Mt Spokane Photography said:


> I had my RF 35mm on my R5 here on my desk and tried taking a photo of a 45 degree slanted ruler with a black sharpie mark at the apparent point of focus. I used magnification of the lcd to place the mark in the center of the AF box.
> 
> My first photo was at f/16, and as expected the entire ruler was in sharp focus at about 2.5 ft more or less. I did not bother to show it.
> 
> ...



Correct.
But it has nothing to do with the fact that in the point of intended focus resolution Dropped Greatly when stopping down , especially to F2,8-5,6.

That meant:
if you want to take a portrait and shoot and have only eyes in focus you shoot at f1,8.
And that was OK
If you want slightly sharper eyes and also maybe ears in focus you plan to shoot at f f4-f 5,6.
BUT alas- when shooting at these apertures there were only ears in focus and eyes were OOF.

And that effect was nonexistent with any EF 35 mm either 2.0 or 1.4, only RF

The sweet point for the point of intended focus of all these lenses including as it is claimed by Canon the RF version is around F5,6.

That is why I added pics of charts and not rulers.
The case with carts was the following:
you shoot from tripod at f 1,8 - you have a sharp chart
you shoot from tripod at f 2,8-5,6 - you have a blurred chart

I hope this time I explained it better!

If you want to try it yourself, just take any package with small letters on it, put it a couple of meters away from the camera, and shoot it first with F1,8, then refocus and shoot with f4. Better to do it several time in different light conditions. Just make sure you do not move the camera. And look at the results. If at F4 you have at least the same sharpness of letters, then I congratulate you! You do not have the problem I have.
So far people here are telling me that I am wrong but no one has yet tried to do the test as I suggest.


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## Chris.Chapterten (Jan 27, 2021)

I had AF issues with an EF 35mm. I had two copies of the EF 35mm f1.4 L ii that refused to focus accurately on my 5Div. Canon tried various repairs but never resolved the issue, eventually giving me a refund.

In my case the focus was not related to f-stop at all so obviously a different issue. It’s just very unfortunate that you have tried multiple lenses with the same issue. Surely it has to be the camera in that case? I own the RF 35mm 1.8 and haven’t shot a lot of images yet, but out of 50 shots taken at and around f3.2 I only had 2 that missed focus. Definitely no back focus issue that I have picked up on yet. I just did a shoot today and took nearly 500 photo with the 35mm around f2.5... so will be sure to report back if it behavesd strangely. But yeah so far so good.


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## Chris.Chapterten (Jan 28, 2021)

Following up. Have just reviewed a few hundred images shot with the RF 35 f1.8 (shot at f2.5). Focus accuracy seems very good. Will have to try stopped down a little more on my next shoot. But yeah, no complaints


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## Sporgon (Jan 28, 2021)

Dmitri_Kahm said:


> Correct.
> But it has nothing to do with the fact that in the point of intended focus resolution Dropped Greatly when stopping down ,
> And that was OK
> If you want slightly sharper eyes and also maybe ears in focus you plan to shoot at f f4-f 5,6.
> ...


I thought that the reviewing world had established that this RF 35/1.8 suffers from RSAs - focus shift, and what you're describing seems to fit with this. If so it's a normal characteristic of the lens and you'll have to learn to work around it just like those of us that have RSA effected lenses such as the EF 50/1.2 & Tamron 85/1.8 VC have to.


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## Chris.Chapterten (Jan 28, 2021)

Sporgon said:


> I thought that the reviewing world had established that this RF 35/1.8 suffers from RSAs - focus shift, and what you're describing seems to fit with this. If so it's a normal characteristic of the lens and you'll have to learn to work around it just like those of us that have RSA effected lenses such as the EF 50/1.2 & Tamron 85/1.8 VC have to.



Very interesting. I had actually missed the focus shift issue in the reviews I had seen on YouTube. The digital picture has a good explanation of it in their review: https://www.the-digital-picture.com/Reviews/Canon-RF-35mm-f-1.8-IS-STM-Macro-Lens.aspx

In my first shoot with the lens I only used f2.0 and f2.5 so that would explain why I wasn’t really experiencing the focus shift issues. It seems most pronounced after 2.8 based on the digital picture review.

How does one compensate for this in real world shooting? I would imagine that adjusting manual focus and bringing the focus point forward would be extremely hit and miss? I’m honestly quite surprised that modern lenses still suffer from this.

It looks like I won’t be using my RF 35 f1.8 at the problem apertures... most likely will keep it at or below f2.5.


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## Sporgon (Jan 28, 2021)

Chris.Chapterten said:


> Very interesting. I had actually missed the focus shift issue in the reviews I had seen on YouTube. The digital picture has a good explanation of it in their review: https://www.the-digital-picture.com/Reviews/Canon-RF-35mm-f-1.8-IS-STM-Macro-Lens.aspx
> 
> In my first shoot with the lens I only used f2.0 and f2.5 so that would explain why I wasn’t really experiencing the focus shift issues. It seems most pronounced after 2.8 based on the digital picture review.
> 
> ...


Well the only work around I have is when using apertures most effected, so those that are small enough to create the issue but not so small as to have enough dof to cover it up - like you say around the f/2.8 mark, is to focus on something that a little closer than I want. Obviously this is risky and not ideal. 

Honestly I'm surprised that given the computing power of modern cameras, when using these lenses, like the EF 50/1.2 for instance, the camera can't be programmed to stop down when using the most effected apertures. Even in live view the EOS won't focus if you are holding the dof button in.


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## Chris.Chapterten (Jan 28, 2021)

Sporgon said:


> Well the only work around I have is when using apertures most effected, so those that are small enough to create the issue but not so small as to have enough dof to cover it up - like you say around the f/2.8 mark, is to focus on something that a little closer than I want. Obviously this is risky and not ideal.
> 
> Honestly I'm surprised that given the computing power of modern cameras, when using these lenses, like the EF 50/1.2 for instance, the camera can't be programmed to stop down when using the most effected apertures. Even in live view the EOS won't focus if you are holding the dof button in.


Thanks. Yeah, it really doesn’t sound like there is much you can do. I would be very reluctant to try and guess where the focus might land like that... very tricky to get right every time.

I have heard that Sony and Nikon mirrorless focus with the lens stopped down, so I’m not sure why canon can’t make this an option? It could even be automatic when an affected lens is detected by the camera.

I did actually just find a few images taken on my most recent shoot that were back focused at f2.5. (Ear instead of eye). These were at a slightly further distance (closer to full length body shots). It wasn’t an entirely consistent behaviour but all of the shots that did miss were slightly back focused (never front focused). I might have to do some tests to see how subject distance affects things with this lens..


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## StoicalEtcher (Jan 28, 2021)

Sporgon said:


> Well the only work around I have is when using apertures most effected, so those that are small enough to create the issue but not so small as to have enough dof to cover it up - like you say around the f/2.8 mark, is to focus on something that a little closer than I want. Obviously this is risky and not ideal.
> 
> Honestly I'm surprised that given the computing power of modern cameras, when using these lenses, like the EF 50/1.2 for instance, the camera can't be programmed to stop down when using the most effected apertures. Even in live view the EOS won't focus if you are holding the dof button in.


Just a thought: Could one use AFMA to counter-act this? i.e. check what adjustment works for you at the given/affected aperture and then in future dial that in when using the lens in question at that/those apertures?


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## Joules (Jan 28, 2021)

StoicalEtcher said:


> Just a thought: Could one use AFMA to counter-act this? i.e. check what adjustment works for you at the given/affected aperture and then in future dial that in when using the lens in question at that/those apertures?


You probably could ... but as far as I'm aware, the RF bodies don't have any AFMA options


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## StoicalEtcher (Jan 28, 2021)

Joules said:


> You probably could ... but as far as I'm aware, the RF bodies don't have any AFMA options


Oh, of course - sorry, I'm still here in DSLR world, and not engaging what's left of my grey matter!
I was thinking of use cases for Ef50 f/1.2 ......
Ignore my post!


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## Sporgon (Jan 28, 2021)

StoicalEtcher said:


> Just a thought: Could one use AFMA to counter-act this? i.e. check what adjustment works for you at the given/affected aperture and then in future dial that in when using the lens in question at that/those apertures?


On a DSLR possibly. The trouble is that for someone like me I'd forget to reset it and then I'd start a thread on CR titled "Terrible front focus of Canon EF 50/1.2"


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## Chris.Chapterten (Jan 28, 2021)

StoicalEtcher said:


> Oh, of course - sorry, I'm still here in DSLR world, and not engaging what's left of my grey matter!
> I was thinking of use cases for Ef50 f/1.2 ......
> Ignore my post!


Unfortunately on a DSLR using the AFMA would only work for a specific subject distance at a specific aputure. It might be useful for a studio setting shooting still life. But for fashion etc. it would certainly ruin the mood of the shoot if the subject was unable to move from their mark.

I’ve done a little more reading on it and some people suggest to focus and then ‘lean back’. None of it sounds very scientific haha


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## Chris.Chapterten (Jan 30, 2021)

Had another shoot today and was using the lens at f2.0, f2.2 and f2.5. With the subject at full body length distance there was quite a bit of focus inaccuracy. Every time it missed it was backfocused.

Strangely at closer distances like 3/4 length, 1/2 length and head and shoulder length, auto focus accuracy was very good. This seams counterintuitive, as I would have assumed the focus shift would be more obvious at closer distances, but the opposite was true for my copy of the lens.

Needless to say I’m going to have to learn some of the limitations of this lens and see if I can figure out the distance at which things go pear shaped with the autofocus. It’s such a shame as I love the image quality otherwise. I’ll be hanging out for the RF 35mm f1.2L... c’mon Canon!


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## Dmitri_Kahm (Jan 30, 2021)

Chris.Chapterten said:


> Had another shoot today and was using the lens at f2.0, f2.2 and f2.5. With the subject at full body length distance there was quite a bit of focus inaccuracy. Every time it missed it was backfocused.
> 
> Strangely at closer distances like 3/4 length, 1/2 length and head and shoulder length, auto focus accuracy was very good. This seams counterintuitive, as I would have assumed the focus shift would be more obvious at closer distances, but the opposite was true for my copy of the lens.
> 
> Needless to say I’m going to have to learn some of the limitations of this lens and see if I can figure out the distance at which things go pear shaped with the autofocus. It’s such a shame as I love the image quality otherwise. I’ll be hanging out for the RF 35mm f1.2L... c’mon Canon!


Well, up until 2,8 the backfocus is pretty tolerable. In the 2,8-5,0 range it is the worst, making these apertures almost unusable. That is very sad.
The only "good" point is that I was right after all when I started this topic despite the claims of some reputable forum members ;-)

The Canon EF 35 2.0 does not suffer from this issue and is still pretty light with similar IQ + it is not STM, but USM. You may try it + converter. I sold my RF and bought EF.


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## Chris.Chapterten (Jan 31, 2021)

Dmitri_Kahm said:


> Well, up until 2,8 the backfocus is pretty tolerable. In the 2,8-5,0 range it is the worst, making these apertures almost unusable. That is very sad.
> The only "good" point is that I was right after all when I started this topic despite the claims of some reputable forum members ;-)
> 
> The Canon EF 35 2.0 does not suffer from this issue and is still pretty light with similar IQ + it is not STM, but USM. You may try it + converter. I sold my RF and bought EF.



Yeah, I had no trouble with f2.0 - f2.5 at closer distances. Focus accuracy was very good. When I got a bit further out it wasn’t too happy. Funnily enough the lens actually reminds me of my old EF 50mm 1.4 in terms of focusing motor behaviour.

At a slightly further distance the RF 35mm f1.8 autofocus tends to jitter back and forth a bit while locking focus. With my L lenses once it has locked focus in single shot AF mode it just stays there. Even if I half press the shutter again, the L lens will only ever make the slightest of movement. I would assume this is because the initial acquisition of focus is more confident /accurate. With the RF 35mm 1.8 there are constant little movements all the way up until the focus locks. If I half press the shutter again without the subject moving it will start jittering back and forth a bit before locking focus. I would assume all of the missed focus were back focused because the lens tends to move in that direction when stopped down a bit anyway. So if the the focus is slightly off, the problem is made worse by using a slightly stopped down aputure?

Did you ever experience more focus motor movement like I described when trying to aquire focus from a slightly further distance?

EDIT: some further details after reviewing a batch of ‘problem images’ taken at a full length body distance at f2.0 and f2.2. Out of 62 photos 18 were backfocused to the point of being practically unusable. A further 5 were backfocused to the point were some sharpening made them acceptable. The remaining 39 were quite good and usable without the need for sharpening.

I should note that all 62 of these images were partially backlit. No direct sun or anything, just an open window with a partial sheer curtain covering. Contrast on the front of the subject was fairly low and settings ranged from ISO 400, f2.2, 1/200 to ISO 400, f2.0, 1/320. Just to give an idea of the light level. In essentially the same lighting conditions my RF 50mm 1.2L and RF 85mm 1.2L did perfectly fine with focus accuracy.

The frustrating thing with the AF inaccuracy on this lens in this particular situation is that I had 8 in a row that were backfocused to the point of being unusable. This meant I missed 3 different poses/expressions from the model (including one I was hoping to use as a final image).


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## Dmitri_Kahm (Feb 1, 2021)

Chris.Chapterten said:


> Yeah, I had no trouble with f2.0 - f2.5 at closer distances. Focus accuracy was very good. When I got a bit further out it wasn’t too happy. Funnily enough the lens actually reminds me of my old EF 50mm 1.4 in terms of focusing motor behaviour.
> 
> At a slightly further distance the RF 35mm f1.8 autofocus tends to jitter back and forth a bit while locking focus. With my L lenses once it has locked focus in single shot AF mode it just stays there. Even if I half press the shutter again, the L lens will only ever make the slightest of movement. I would assume this is because the initial acquisition of focus is more confident /accurate. With the RF 35mm 1.8 there are constant little movements all the way up until the focus locks. If I half press the shutter again without the subject moving it will start jittering back and forth a bit before locking focus. I would assume all of the missed focus were back focused because the lens tends to move in that direction when stopped down a bit anyway. So if the the focus is slightly off, the problem is made worse by using a slightly stopped down aputure?
> 
> ...



Hello! Unfortunately I do not remember, how my RF 35 behaved in terms of "little movements" you mention. Probably, mine was behaving the same. But I feel that the USM focus motor the EF2.0 version has is anyway better and quicker than STM of RF 35. Moreover, there are no external moving parts is EF 2.0.


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