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

[jd7]

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.

 

[Kit Lens Jockey]

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.

 

[Frodo]

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.

 

[Chris.Chapterten]

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?

 

[Frodo]

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......?

 

[Frodo]

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.

 

[Chris.Chapterten]

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.

 

[Pape]

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*

 

[SecureGSM]

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?

 

[Frodo]

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.

 

[deleteme]

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.

 

[Pape]

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

 

[deleteme]

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.