# I noticed the EOS R sometimes stops down lenses during focusing, what's the deal with that?



## Kit Lens Jockey (Jan 24, 2019)

I just noticed when using both an EF 50mm 1.2L and an EF 50mm 1.0L on the EOS R that the camera actually stops down the lens while it's attempting to autofocus in moderately bright conditions. If you have the aperture set wide open, it opens back up to actually take the photo. It will even stop down the lens when you aren't trying to focus by just pointing it at a bright source of light. If you focus under pretty dim lighting, the lens doesn't stop down. This seems kind of weird. I wonder why this happens. Apparently under some conditions there's just too much light hitting the sensor for it to focus properly? I do wonder how it can possibly nail focus at a wide aperture if it's not actually at the wide aperture when it's autofocusing.


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## Larsskv (Jan 24, 2019)

One theory I have is that the EF 50L is so soft at f1.2 that it the dual pixel AF doesn´t focus very well at that aperture... It could therefore be programmed to stop down, in order to focus better. On the other hand though, I found the EF 50L + the EOS R to focus very badly at f3.5, not compensating for the focus shift on the 50L. Before that I had used the EF 50L on the 1DXII and 5DIV, and never experienced the focus shift issue. It seems to me that the 1DXII and 5DIV compensates for it, while the EOS R doesn't. This was just an impression I got. I didn't test this very thoroughly because I sold the EF50L as soon as I got the RF50L...


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## Kit Lens Jockey (Jan 24, 2019)

I don't know that I buy what you're saying about the camera not being able to focus wide open. After all, it will focus wide open in low light. But in a well lit room, then it stops down.

Also, your experience with the EOS R not focusing accurately is absolutely opposite of my own, and most other peoples' that I've read. The EOS R is focusing using the image on the sensor itself, not a separate autofocus sensor like DSLRs. Why would the supposed "focus shift" of a lens even matter on a mirrorless? The camera is just going to move the focus until the _actual image_ is in focus. That's why Canon has done away with the AFMA settings on the EOS R. (And also why I'm very confused that Sony still has those settings on their cameras.) There's really no point to them any more. If your EOS R isn't focusing accurately, there's something really wrong with your camera or lens.


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## Mt Spokane Photography (Jan 25, 2019)

Kit Lens Jockey said:


> I don't know that I buy what you're saying about the camera not being able to focus wide open. After all, it will focus wide open in low light. But in a well lit room, then it stops down.
> 
> Also, your experience with the EOS R not focusing accurately is absolutely opposite of my own, and most other peoples' that I've read. The EOS R is focusing using the image on the sensor itself, not a separate autofocus sensor like DSLRs. Why would the supposed "focus shift" of a lens even matter on a mirrorless? The camera is just going to move the focus until the _actual image_ is in focus. That's why Canon has done away with the AFMA settings on the EOS R. (And also why I'm very confused that Sony still has those settings on their cameras.) There's really no point to them any more. If your EOS R isn't focusing accurately, there's something really wrong with your camera or lens.




Focus shift is a concern if a camera focuses wide open and then stops the lens down. Being mirrorless does not change that. If the camera focuses at the same aperture as the shot, then focus shift is not a issue. 

I have not tried to determine if my R focuses stopped down, or wide open just before stopping down, I'd have to do some experiments to see and try to figure out what its doing.


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## Kit Lens Jockey (Jan 25, 2019)

I did not realize focusing shifts at different apertures.

I can definitely confirm that with wide aperture primes, the lens actually stops down to focus, then opens back up to take the shot under fairly bright lighting conditions. (A well lit room, indoors.) When I discovered this, I was taking photos with the aperture set wide open, so I thought it was strange that it was stopping down at all.


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## Mt Spokane Photography (Jan 25, 2019)

Kit Lens Jockey said:


> I did not realize focusing shifts at different apertures.
> 
> I can definitely confirm that with wide aperture primes, the lens actually stops down to focus, then opens back up to take the shot under fairly bright lighting conditions. (A well lit room, indoors.) When I discovered this, I was taking photos with the aperture set wide open, so I thought it was strange that it was stopping down at all.


Only lenses with a lot of spherical aberration are a significant issue, and only when a large change of aperture is involved. The Canon EF 50mm f/1.2 is a example. The Canon RF 50mm f/1.2 has much less spherical aberration and does not show the issue as being significant, but a little is still there.

https://photographylife.com/what-is-focus-shift


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## Larsskv (Jan 25, 2019)

Kit Lens Jockey said:


> I did not realize focusing shifts at different apertures.
> 
> I can definitely confirm that with wide aperture primes, the lens actually stops down to focus, then opens back up to take the shot under fairly bright lighting conditions. (A well lit room, indoors.) When I discovered this, I was taking photos with the aperture set wide open, so I thought it was strange that it was stopping down at all.



Focus shift means that the plane of focus moves when the lens stops down. Therefore, if not corrected for, an EF 50 L (which has focus shift issues) which is in perfect focus at f1.2 will miss focus at approximately f2.8-f4.

Please, also note that few forum members has praised the EOS R focus accuracy with large aperture lenses more than I have.


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## Kit Lens Jockey (Jan 25, 2019)

Ok, I'll note that, but you just said that you found the EF 50L + the EOS R to focus very badly at f3.5.

So you're saying that the EOS R has good focus accuracy with large aperture lenses when used wide open, but sometimes not when those large aperture lenses are stopped down?


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## Larsskv (Jan 25, 2019)

Kit Lens Jockey said:


> Ok, I'll note that, but you just said that you found the EF 50L + the EOS R to focus very badly at f3.5.
> 
> So you're saying that the EOS R has good focus accuracy with large aperture lenses when used wide open, but sometimes not when those large aperture lenses are stopped down?



It is the EF50L that suffers from focus shift. I am not aware of any other L prime that has focus shift issues. 

Another lens that has focus shift is the EF24-70 f4, but you will rarely notice it because of the smaller apertures. 

As I stated, when using 1DXII and 5DIV I never had focus shift issues with the EF50L. I believe those bodies compensates for it during AF. But the focus shift issue is real and has been used for bashing the EF50L for many years.


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## Larsskv (Jan 25, 2019)

Kit Lens Jockey said:


> Ok, I'll note that, but you just said that you found the EF 50L + the EOS R to focus very badly at f3.5.
> 
> So you're saying that the EOS R has good focus accuracy with large aperture lenses when used wide open, but sometimes not when those large aperture lenses are stopped down?



By the way, I never tried the EF50L and the EOS R in good daylight, so it can very well be so that in good light it stops down when focusing, and therefore doesn’t change aperture when it takes the shot. If so, there will be no focus shift.


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## Mt Spokane Photography (Jan 26, 2019)

Larsskv said:


> By the way, I never tried the EF50L and the EOS R in good daylight, so it can very well be so that in good light it stops down when focusing, and therefore doesn’t change aperture when it takes the shot. If so, there will be no focus shift.


If you focus the lens at f/5.6 and then shoot at f/1.2, the focus point will change with the 50L. The same happens with a DSLR, but in reverse, they focus wide open, and then if you have it set to shoot at f/5.6 the focus point will shift.

One of the reasons to buy a 50L is the wide aperture, if you focus it with a DSLR and then shoot at f/1.2, there is no focus shift, but because the "R" stops down to focus, shooting a 50L at a wide aperture will result in focus issues. I'd highly recommend selling any 50L you own and getting the RF 50 1.2 if you plan to do a lot of photos at fast apertures. The lens is very good, there are very few mirrorless lenses to compete with it, so in its class, it stands out. We'll see how the new Nikon lens does when it hits the streets, it may be even more exceptional.


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## jd7 (Jan 26, 2019)

For what it's worth, everything else I've read on the internet is that the EF 50 1.2L focuses very accurately on the EOS R. 

This Steve Huff webpage is one example of the sort of thing I've read
http://www.stevehuffphoto.com/2018/10/21/that-old-canon-50-f-1-2-ef-rocks-on-the-eos-r/

If the EOS R is stopping down to AF and then opening the aperture to shoot, and that's causing focus shift, I'm surprised at the number of times I've read how well the EF 50 1.2L works with it. 

Anyone here got an EOS R and an EF 50L to do some testing?


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## killswitch (Jan 26, 2019)

I have been using EF 50 1.2 with my R. I think it does tend to have soft focus as it stops down. I never realized till I read this thread. I have to check my files again, but I remember I took a bunch of shots of my 1.5 year old son at fast shutter speed and wide open. The focus acquiring seemed fast but pictures looked ever so slightly out of focus. It doesn’t appear that way at first unless you are really looking for it. It seems either the focal plane shifted a tad or the AF point that was used was slightly off target (due to user error maybe).


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## Larsskv (Jan 26, 2019)

Mt Spokane Photography said:


> If you focus the lens at f/5.6 and then shoot at f/1.2, the focus point will change with the 50L. The same happens with a DSLR, but in reverse, they focus wide open, and then if you have it set to shoot at f/5.6 the focus point will shift.
> 
> One of the reasons to buy a 50L is the wide aperture, if you focus it with a DSLR and then shoot at f/1.2, there is no focus shift, but because the "R" stops down to focus, shooting a 50L at a wide aperture will result in focus issues. I'd highly recommend selling any 50L you own and getting the RF 50 1.2 if you plan to do a lot of photos at fast apertures. The lens is very good, there are very few mirrorless lenses to compete with it, so in its class, it stands out. We'll see how the new Nikon lens does when it hits the streets, it may be even more exceptional.



I thought it was obvious that if the R stops down to focus, then it stops down to the intended aperture you shoot with, and that it wouldn’t open up again to take the shot. 

Btw, I own the RF50L. It is amazing.


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## Viggo (Jan 26, 2019)

One might think the EF 50 L doesn’t have focus shift, and it was also some talk years ago that a 2010 version, and perhaps later were actually better etc. All not true, it lacks floating elements like the 85 f1.2 L does have so every single copy shows the exact same focus shift between f2.0-f4, better faster than f2 and from 5.6. It may also Show more or less depending on focusing distance.

The reason it might show better with the R, is that it stops down to focus when shooting wide open. And the other is that the AF with the R is incredibly precise showing ANY issues better than any other DSLR . Miscalibrate the EF 50 L slightly and it hides this issue to a certain degree. With the R being 100% accurate it will show. Combine those two things and the R will reveal focus shift a lot more, but it’s always there. One copy of the lens is not better than another one.


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## Kit Lens Jockey (Jan 26, 2019)

Well, now I've noticed that its behavior when focusing seems totally random. Sometimes it stops down, sometimes it doesn't. Sometimes it does or doesn't under similar circumstances. Is anyone else seeing this? I'm perplexed.


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## Mt Spokane Photography (Jan 27, 2019)

I have my camera here, set to Fv with a f/8 aperture, ISO 100, servo AF and face det AF. With those settings, it focuses wide open and stops down to shoot. I then put it in the P position and it does the same. I have a very old 50mm f/2.5 lens mounted on it right now, my other lenses are not here with me, well, my 100mm L is around here, I guess.
I could try other lenses and settings, maybe another day. I no longer use fast primes, so I can't check them.


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## Viggo (Feb 7, 2019)

I was trying something in M mode and noticed something I don’t get ; when shooting with a dark frame and Exp.Sim on it won’t open the aperture to focus, so when for example I choose f11 1/4000s indoors it just hunts. When I turn exp.sim off, it focuses normally. How is that not a bug?


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## YuengLinger (Feb 7, 2019)

So does the R stop down to focus? Always? Some conditions?


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## Kit Lens Jockey (Feb 8, 2019)

Seems very random when it does. I've seen it a few times with fast primes, but then I also saw it the other day using a Tamron 24-70 2.8. Although, I was shooting towards the direction of the sun when it did this, so that's kind of understandable. I just sort of wonder _why_ it's doing this.


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## jd7 (Feb 9, 2019)

Kit Lens Jockey said:


> Seems very random when it does. I've seen it a few times with fast primes, but then I also saw it the other day using a Tamron 24-70 2.8. Although, I was shooting towards the direction of the sun when it did this, so that's kind of understandable. I just sort of wonder _why_ it's doing this.


Perhaps something to do the image sensor being exposed the whole time during focusing on a mirrorless (and any other time the camera is active I guess) and a possibility bright light might damage the sensor? I'm sure I've seen claims that extended exposure to a light source such as the sun can damage a sensor. And I think I read something about Canon saying not to point the EOS R at the sun for too long ... although I just did a wick Google search now and couldn't find it so maybe I'm confused.


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## Kit Lens Jockey (Feb 11, 2019)

I think you might be right. I was just thinking about this the other day when I was photographing a sunset and how nice it was that I didn't have to worry about damaging my eye when looking at the sun through a mirrorless camera. But then I also realized that what it could potentially do is damage the sensor. So this might be a protection strategy for the camera. (It didn't stop down in this particular instance that I can remember, but it was a very hazy sunset, the sun wasn't very bright.


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## Frodo (Apr 19, 2020)

I just had a similar problem today. Both with the 85/1.8 and 200/2.8L. I noticed that the viewfinder was darkish (I have exposure simulation switched off). I was shooting at f/2.8 and f/4, but the lens seemed to be stopped down to about f/8. It then opened up to f/2.8 or f/4 (whichever I had set) when shooting. Exposures were fine, but most of the 200/2.8 shots were slightly out of focus, some unusable. I removed the battery, but the problem persisted. The only difference that I noted was that I used a 32 GB Lexar 633x 95MB/s card instead of my Sony Tough When I removed it from the card reader, I noticed this physical damage. I'm hoping that this is what caused my problem. The card is going in the trash.


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## Chris.Chapterten (Apr 20, 2020)

Frodo said:


> I just had a similar problem today. Both with the 85/1.8 and 200/2.8L. I noticed that the viewfinder was darkish (I have exposure simulation switched off). I was shooting at f/2.8 and f/4, but the lens seemed to be stopped down to about f/8. It then opened up to f/2.8 or f/4 (whichever I had set) when shooting. Exposures were fine, but most of the 200/2.8 shots were slightly out of focus, some unusable. I removed the battery, but the problem persisted. The only difference that I noted was that I used a 32 GB Lexar 633x 95MB/s card instead of my Sony Tough When I removed it from the card reader, I noticed this physical damage. I'm hoping that this is what caused my problem. The card is going in the trash.
> View attachment 189906


Interesting.. but I'm not sure how a damaged card could have caused a focusing issue?


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## Frodo (Apr 20, 2020)

Chris.Chapterten said:


> Interesting.. but I'm not sure how a damaged card could have caused a focusing issue?


Yeah, Chris, I can't figure that out either. But I shot another 80 photos under the same conditions today without a problem. I googled my symptoms and this was the only thread that had the same problem. Just seems too much of a coincidence......?


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## Frodo (Apr 25, 2020)

The problem happened again with a Sony card. I thought a card was unlikely to cause this, but a coincidence? 
My current thinking is that it is a mechanism built into the camera to protect the sensor when shooting wide apertures in bright sunlight. Still a bit of a pain as it seems to reduce focusing accuracy.


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## Chris.Chapterten (Apr 25, 2020)

Frodo said:


> The problem happened again with a Sony card. I thought a card was unlikely to cause this, but a coincidence?
> My current thinking is that it is a mechanism built into the camera to protect the sensor when shooting wide apertures in bright sunlight. Still a bit of a pain as it seems to reduce focusing accuracy.


That's a real shame about the focus accuracy suffering. Are the EF lenses you are using known to have any focus shift issues? I wonder if this is a problem when using RF lenses? It seems like a major system flaw if this happens with all lenses... I haven't tested my EOS R in the sun yet so don't have any experience with the issue.


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## Pape (Apr 25, 2020)

Horrible and silenced truth about R cameras is ,they not using dpaf.
They just use viewfinder data to focus picture. 
Nobody believes it would work so they wont tell it  
*wears tinhat and goes hide under bed*


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## SecureGSM (Apr 25, 2020)

Pape said:


> Horrible and silenced truth about R cameras is ,they not using dpaf.
> They just use viewfinder data to focus picture.
> Nobody believes it would work so they wont tell it
> *wears tinhat and goes hide under bed*


Say what?


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## Frodo (Apr 25, 2020)

Chris.Chapterten said:


> That's a real shame about the focus accuracy suffering. Are the EF lenses you are using known to have any focus shift issues? I wonder if this is a problem when using RF lenses? It seems like a major system flaw if this happens with all lenses... I haven't tested my EOS R in the sun yet so don't have any experience with the issue.


I'll have to do a more thorough investigation of this issue. I noticed the the issue with the 85/1.8 and 200/2.8L lenses shooting at distances of several yards and more (groups). I've not noticed focus shift in the R or 5DsR. But, if its focusing at f/5.6 and shooting at f/2.8, slight AF inaccuracy is to be expected. I've googled this and was surprised that this thread is the only one that covers the issue.


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## deleteme (May 2, 2020)

Frodo said:


> The problem happened again with a Sony card. I thought a card was unlikely to cause this, but a coincidence?
> My current thinking is that it is a mechanism built into the camera to protect the sensor when shooting wide apertures in bright sunlight. Still a bit of a pain as it seems to reduce focusing accuracy.


I think this is exactly the issue. In bright situations I have noticed that the image darkens to focus or in dim situations it will brighten to focus. In both cases I believe that the sensor AF works best in a certain range of brightness. With exp sim you will see this but not with it disabled. Thus the 50L will focus wide open in low light but stop down to shooting aperture in bright light. 
Just my .02 as I don't own the lens.


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## Pape (May 2, 2020)

Seen also when exposure simulation is too dark RP got difficulties to focus.When increasing exposure time focus locks good.


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## deleteme (May 4, 2020)

Frodo said:


> When I removed it from the card reader, I noticed this physical damage. I'm hoping that this is what caused my problem. The card is going in the trash.
> View attachment 189906


I had this issue of the ribs breaking when I first used SD cards several years ago. Normally I didn't have an issue as I never removed the SD, only the CF. I looked around and noticed that many, if not most, have abandoned this form for the far more reliable smooth surface as done in the Sony Tough and others.
I cannot imagine what they were thinking. I have never had a CF card bend pins or fail mechanically. But a tiny rib breaking off in the SD slot would enrage me no end; Especially if I was using an R with only one slot.


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