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

Dmitri_Kahm

I'm New Here
Oct 10, 2020
24
3
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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Last edited:

Viggo

EOS R5
Dec 13, 2010
4,780
1,467
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

Moderator
CR Pro
Dec 11, 2018
8
5
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.

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

I post too Much on Here!!
CR Pro
Mar 25, 2011
16,698
1,665
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.
 

Dmitri_Kahm

I'm New Here
Oct 10, 2020
24
3
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.
 

SHAMwow

EOS M6 Mark II
CR Pro
Sep 7, 2020
52
87
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.
 

Dmitri_Kahm

I'm New Here
Oct 10, 2020
24
3
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.
 

SHAMwow

EOS M6 Mark II
CR Pro
Sep 7, 2020
52
87
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.
 

YuengLinger

EOS R5
CR Pro
Dec 20, 2012
3,516
1,961
USA
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:

 
Jan 24, 2021
1
0
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.
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.
 

YuengLinger

EOS R5
CR Pro
Dec 20, 2012
3,516
1,961
USA
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?
 

Dmitri_Kahm

I'm New Here
Oct 10, 2020
24
3
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?

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

EOS R5
CR Pro
Dec 20, 2012
3,516
1,961
USA
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?
 

Dmitri_Kahm

I'm New Here
Oct 10, 2020
24
3
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?
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.
 

YuengLinger

EOS R5
CR Pro
Dec 20, 2012
3,516
1,961
USA
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.
 

Mt Spokane Photography

I post too Much on Here!!
CR Pro
Mar 25, 2011
16,698
1,665
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.


EMWL0181.jpg
EMWL0183.jpg



2_5 ft f2.JPG


7ft.JPG


15ft.JPG
 

Dmitri_Kahm

I'm New Here
Oct 10, 2020
24
3
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.


View attachment 195519 View attachment 195520


View attachment 195524

View attachment 195525

View attachment 195526

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. :)
 
Last edited:
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Feb 15, 2020
535
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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.
 
Feb 15, 2020
535
369
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
 

Sporgon

5% of gear used 95% of the time
CR Pro
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.
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
............
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.