Archive 2021 · Canon 6D & R6: aperture stops down itself during liveview in bright ...

Deathchant
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p.1 #1 · Canon 6D & R6: aperture stops down itself during liveview in bright conditions

After having contact with Canon CPS, Zeiss technical services and fellow youtuber Dustin Abbott without any satisfying result, I am turning to you guys to ask for your help in solving/reproducing an issue. Still awaiting feedback on DPreview though, as I've sent them the same post as below.

Since the Canon 6D, I experience issues with miss-focused shots while there is no chance of camera shake, too slow shutter speeds or unreliable auto-focus, front/back focus that could cause this. It happens also during manual focus on a tripod with shutter speeds of > 1/1600.

I found the root cause of the miss focus: during liveview, the aperture of all my lenses randomly stop down to let's say around f/8 while settings on Av-mode (or in any mode for that matter) are set to f/2.
This seems to happen mostly when there are bright conditions. How bright it must be in order to reproduce it, I cannot yet pinpoint but it is easily reproduced by pointing the camera to my phone flashlight or pointing to a light bulb. It also happens even if the light source is just barely in the frame, especially with my 135/2 APO sonnar. That lens seems to be the most sensitive.

Accurately manual focus with a shallow depth of field even in magnify is tricky: you think you are focusing with a DoF of f/2 while your camera stops it down to f/8 due to bright light. This means when focusing on a subject at f/2, let's say a nearby tree, I have a very short focus throw in which the tree goes in and out of focus. If the camera stops the aperture down to around f/8 by itself due to bright conditions, I also see the DoF of f/8 in the EVF/LCD meaning there is a long focus throw in which the tree stays in focus. So, I think I focused tack sharp on the tree, but the end result is not tack sharp and often not sharp at all due to thinking I focused with the f/2 DoF while it was f/8 during liveview.
With my Zeiss lenses it happens the most, those lenses also have a more noisy aperture, so I can always hear it when it opens and closes.

In order to mitigate this, I have to always hold down the dof-preview button during composition in bright conditions, which usually closes the aperture to the setted value, but in my case f/2, resulting in actually opening it back again to f/2. The camera should always use the widest aperture in liveview and should only stop down when you press the DoF-preview button. That's what every manual says.

You would think it is the Exposure Simulation setting, but it doesn't matter which settings you set on any dials on the camera or Exposure Simulation or Safety Shift: it always happens during bright conditions, especially with my f/2 Zeiss lenses (50 Makro-Planar, 100 Makro-Planar and 135 Apo Sonnar).
It also happens with my 16-35/4L IS and 70-200/2.8L II, although less frequent.
My guess is that it depends on how bright the scene is and how fast the lenses are.

Canon CPS said that the 6D is a "first gen liveview camera" that should not be used for professional purposes.
Zeiss told me that it is normal behavior for the aperture to stop itself down in order to show a proper liveview.
I even bought a Canon EOS R6 out of frustration but the same behavior is present.

I've looked through the dpreview forum, tweakers.net but no one seems to experience this issue.
I have a feeling it has something to do with light metering algorithms...

Can you help me with this issue, reproduce it or find out if this is really a bug or a works-as-designed thingy? It is really driving me crazy not knowing why the cameras have this behavior. It seems this could be easily fixed by a firmware update.

EDIT: I've made a small video of this erratic aperture behavior on my old 6D and 135 apo when liveview was enabled. You can hear the aperture clicking. I've uploaded it to flickr so here is the link:

Erratic aperture behavior in liveview during bright conditions

You can clearly see that when pointing to the light source behind me it is closing and if I point it towards myself (dark tshirt) it opens up again. This behavior is also present on the R6.

Nov 04, 2021 at 11:13 AM

Toothwalker
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p.1 #2 · Canon 6D & R6: aperture stops down itself during liveview in bright conditions

I have noticed the same behavior, with the same two cameras, and with both Zeiss and Canon lenses. It is more obvious with Zeiss, since, as you write, you can hear it happening.

Here is a quote from Zeiss:

And there is also a �fly in the ointment� when it comes to the use of the Live View function, namely the fact that many current camera models (e.g. the Nikon D700 and the Canon EOS 5D MkII) automatically control the aperture in the Live View mode based on the set ISO values and the ambient light in order to ensure that the image in the display is consistently shown with the correct brightness and contrast values. This means that it is no longer possible to close the aperture to the desired, fixed setting using the preview button. Correct evaluation of the depth of field and focus position is therefore equally out of reach using this method, since the aperture is only closed to the desired setting when the shot is actually taken.

Edit: Googling the Zeiss quote, I see that we are not the only ones. But there is surprisingly little to find on this topic.

Nov 04, 2021 at 12:20 PM

amacal1
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p.1 #3 · Canon 6D & R6: aperture stops down itself during liveview in bright conditions

I have noticed this behavior with my EOS R since I very first started using it. It's most obvious with my EF 70-200mm f/2.8L IS (ver. I), but this is most likely because I have used this lens the most when outside shooting my kids' soccer games. Also, everything that lens does is super loud, including stopping down the aperture, so I can hear it doing it constantly.

It used to freak me out, because it would do it most when I moved from holding the lens/camera vertically to holding it horizontally or vice-versa. I would occasionally wonder if I was having an issue with the lens or adapter flexing and causing issues with lens contacts was behind it, but that was just a silly notion. Was never able to really tell why it did it, but I just ignored it and haven't thought about it in a while.

Nov 04, 2021 at 03:15 PM

Deathchant
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p.1 #4 · Canon 6D & R6: aperture stops down itself during liveview in bright conditions

Toothwalker wrote:
I have noticed the same behavior, with the same two cameras, and with both Zeiss and Canon lenses. It is more obvious with Zeiss, since, as you write, you can hear it happening.

Here is a quote from Zeiss:

And there is also a �fly in the ointment� when it comes to the use of the Live View function, namely the fact that many current camera models (e.g. the Nikon D700 and the Canon EOS 5D MkII) automatically control the aperture in the Live View mode based on the set ISO values and the ambient light in order to ensure that...Show more →
You are a life saver! You have no idea how long I am struggling with this issue and I could not seem to find people with the same issues, but the link you provided with the guy that had the exact same issue at least does not make me feel so alone in this. It is posted here on Fredmiranda too

I should have registered with Fredmiranda much earlier, but for some reason I didn't. In fact, Fredmiranda, especially the ZM/ZE Zeiss phototopic made me all gung-ho about the Zeiss 3D effect, because that's what I was looking for.

Anyway, it also kinda bums me out knowing there will most likely not be a solution anytime soon, since the guy with the same issue has addressed it over 5 years ago, but it is still present.

I am wondering if it is limited to a certain set of camera's...The 5Ds seems to have that logic to stop down the aperture based on the brightness of ambient lighting conditions. The 6D has it, the R6 has it....

Since it seems a liveview-based issue, I would expect to see more cases with the revolution of mirrorless, because mirrorless is in fact 100% liveview (including EVF) and has no OVF.
It's a tricky issue to recognize because you are most likely to see miss focused shots when using narrow DoF's with tele lenses and close subjects. If the subject is further away you would still perceive it as "sharp enough", while not knowing it should be way sharper.
I know the camera also stops down the aperture with a Zeiss 21/2.8 distagon attached during bright conditions, but you are less likely to have miss-focused shots due to the field of view being wide and your subject will be in the plane of focus anyway.

This was the reaction I got from Zeiss:
According to our experience, this is a normal behaviour of the aperture in LiveView even of newer Canon SLR cameras.

In stronger sourrounding light, the camera automatically closes the aperture to display a better live image.
However, this aperture is not used later for shooting, but only for the LiveView preview.

We cannot therefore explain why this effect should cause blurred photos.
If necessary, you are welcome to send us one or two example pictures.

With other lenses (Canon), this effect is usually not noticeable or only very slight, as the apertures in the zoom lenses are much smaller and may also...Show more →
Not the answer I was expecting, but they seem to know more about Canon bodies than Canon themselves.
And if it is really true that it has something to do with showing a correct exposed image on the LCD/EVF also contrast-wise, then why the hell is it not linked to the Exposure Simulation setting? This is exactly what you would expect from this setting isn't it?

Sure, there is a workaround you can do when it happens: during manual focusing press down the DoF-preview (this opens up the aperture again to the setted value), do your focusing, release the DoF-preview button, press down shutter.
And yes, adding an ND filter is also a viable workaround which "tricks" the camera into thinking it is not so bright, thus not stopping down the aperture.

The point is: it should not be necessary to deal with workarounds or filters or whatever. It's a really annoying issue which is still not being recognized by Canon, and it's frustrating to no end. It sometimes makes me want to fully change to the Sony or Nikon camera system just to get rid of this nonsense. I thought that before when switching from 6D to R6, but alas. At least I could buy the Voigtlander 65/2 Apo Lanthar

Nov 04, 2021 at 03:24 PM

jeffbuzz
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p.1 #5 · Canon 6D & R6: aperture stops down itself during liveview in bright conditions

Yes, the behavior you describe certainly exists. The camera sensor has a base sensitivity. When illumination hitting the sensor is low, a camera can amplify the signal to boost the output to the viewfinder. This is just like you increasing the ISO setting. If the illumination is too high, there is nothing the camera hardware or software can do to reduce the signal below the base sensitivity. At that point it has to use the lens aperture to further limit incoming illumination to a point where the signal is within the range the sensor can accommodate. The camera is trying to emulate what your eye did when viewing through an optical viewfinder. If you point an SLR at the sun your eye's iris will close down.

I saw this automatic aperture closing much more with Fuji cameras. Likely this is due to them having a higher base ISO. I still see it on the Canon R5/R6 but it seems to require much brighter light to trigger. Probably because the sensor base ISO is lower on the Canon bodies. I also see it more frequently with brighter lenses. They are letting in much more light and the sensor will more easily become saturated requiring the aperture to be stopped down to prevent the signal from being totally washed out.

Could a mirrorless camera operate without using the lens aperture to control the display output? In theory, yes. But it would require sensor technology that currently does not exist or at least is not accessible to consumer camera makers. You'd need a sensor with base ISO 1 and max ISO 1,000,000,000,000. It will be available for holiday season in the year 2159 with a starting price of 37 bitcoins ($2,000,000,000,000 adjusted for inflation). Toilet paper will cost 37.5 bitcoins that year.

Nov 05, 2021 at 11:43 AM

EB-1
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p.1 #6 · Canon 6D & R6: aperture stops down itself during liveview in bright conditions

jeffbuzz wrote:
Yes, the behavior you describe certainly exists. The camera sensor has a base sensitivity. When illumination hitting the sensor is low, a camera can amplify the signal to boost the output to the viewfinder. This is just like you increasing the ISO setting. If the illumination is too high, there is nothing the camera hardware or software can do to reduce the signal below the base sensitivity. At that point it has to use the lens aperture to further limit incoming illumination to a point where the signal is within the range the sensor can accommodate. The camera is trying...Show more →

Some video cameras have built-in ND filters. It's probably not economical or practical with current R series bodies. Maybe that will be implemented in an R1.

EBH

Nov 05, 2021 at 11:56 AM

Deathchant
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p.1 #7 · Canon 6D & R6: aperture stops down itself during liveview in bright conditions

jeffbuzz wrote:
Yes, the behavior you describe certainly exists. The camera sensor has a base sensitivity. When illumination hitting the sensor is low, a camera can amplify the signal to boost the output to the viewfinder. This is just like you increasing the ISO setting. If the illumination is too high, there is nothing the camera hardware or software can do to reduce the signal below the base sensitivity. At that point it has to use the lens aperture to further limit incoming illumination to a point where the signal is within the range the sensor can accommodate. The camera is trying...Show more →
Haha! Wiping the rear with golden toilet paper would be cheaper

You bring it with a sense of humor, but I do really appreciate your answer. It makes sense what you're saying about the translation of illumination signal to LCD/EVF. In the back of my mind, I always thought it was something like this. Now, I see reason WHY it works like this, but I think it is still a "flaw"; if the camera is programmed to just show the correct signal-to-LCD/EVF-image, I would like to see the washed-out'ness on the LCD. At least I then know that the shot will be probably over exposed.
I would've understand if the camera closes the aperture when the shutter speed goes over 1/8000 (it starts blinking when it will be over exposed), but the camera already seems to do it when it is at ISO100 f/2 and 1/2000.

An ND-filter could be a workaround yes, but the question is: how many stops ND filter? What if I had an f/1.4 lens? A 3 stops might not trick the camera enough thinking it can leave the aperture open.

Nov 05, 2021 at 04:58 PM

EB-1
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p.1 #8 · Canon 6D & R6: aperture stops down itself during liveview in bright conditions

Deathchant wrote:
I would've understand if the camera closes the aperture when the shutter speed goes over 1/8000 (it starts blinking when it will be over exposed), but the camera already seems to do it when it is at ISO100 f/2 and 1/2000.

The shutter speed to be used for the image capture is irrelevant to the issue.

EBH

Nov 05, 2021 at 05:08 PM

Deathchant
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p.1 #9 · Canon 6D & R6: aperture stops down itself during liveview in bright conditions

I finally got answers from Canon CPS NL who also asked their European colleagues and the short answer is:
it's not a bug, it's a feature, and it is exactly like @jeffbuzz described.
It will not be "fixed" in a firmware-update because it works as designed, in order to keep the sensor away from damage due to very bright exposures.

In the mean while, a friend of mine tested his EF 70-200/2.8L II on his R6 and it has the same behavior.

This means, I've spent years working around this problem by pressing the DoF preview button which opens up the aperture when the camera closes it during too bright conditions, and it seems I have to live that, or buy an ND filter.

Since the effect is pretty hefty with my Zeiss f/2 lenses, I really wonder what brighter lenses will do....I guess my camera will consider an overcast day as too bright if I attach an RF 50/1.8 to it, let alone an RF 50/1.2......

Nov 18, 2021 at 09:30 AM


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