topic Re: EOS 6D Mark II Conflicts between viewfinder focusing and Live View focusing in EOS DSLR & Mirrorless Cameras

EOS 6D Mark II Conflicts between viewfinder focusing and Live View focusing

Skip70 — Fri, 18 Apr 2025 15:10:13 GMT

Canon 6D Mark II
I am using the Tamron Tap-In console to do micro-focusing on what is now my all stable of Tamron lenses. I am finding a very obvious difference between focus points using the viewfinder and reference focus point using touch screen Live View.

I will try to attach the photos to this post, but the first time using the regular viewfinder focus (spot focus and metering)the focus point) was front focus. I adjusted using the console forward, just as you would with there Canon micro-focus system. However, when I did the same shot zooming in on LiveView, the focus point was clearly back focus, reflecting the influence of my adjustments.

The simplest way say this is that the camera is finding a different focus point on the viewfinder method than it is finding using LiveView. While there is always adjustment we can make on a lens, I'm concerned that there is an issue with the camera.

Ideas?

Re: EOS 6D Mark II Conflicts between viewfinder focusing and Live View focusing

jrhoffman75 — Fri, 18 Apr 2025 19:43:25 GMT

@Skip70 wrote:

Canon 6D Mark II
I am using the Tamron Tap-In console to do micro-focusing on what is now my all stable of Tamron lenses. I am finding a very obvious difference between focus points using the viewfinder and reference focus point using touch screen Live View.

I will try to attach the photos to this post, but the first time using the regular viewfinder focus (spot focus and metering)the focus point) was front focus. I adjusted using the console forward, just as you would with there Canon micro-focus system. However, when I did the same shot zooming in on LiveView, the focus point was clearly back focus, reflecting the influence of my adjustments.

The simplest way say this is that the camera is finding a different focus point on the viewfinder method than it is finding using LiveView. While there is always adjustment we can make on a lens, I'm concerned that there is an issue with the camera.

Ideas?

Camera focusing through the viewfinder uses a different focusing system in the camera than Live View.

Canon’s Free AutoFocus MicroAdjustment Guidebook

eos6d-mk2-im4-en.pdf See page 491.

Re: EOS 6D Mark II Conflicts between viewfinder focusing and Live View focusing

Skip70 — Fri, 18 Apr 2025 20:19:10 GMT

I am aware of that, but they should agree when pointed to exactly the same focus point at the same distance.

Re: EOS 6D Mark II Conflicts between viewfinder focusing and Live View focusing

jrhoffman75 — Fri, 18 Apr 2025 20:35:59 GMT

Why should they? If the viewfinder focusing system is out of adjustment then it will, by definition, be out of focus compared to Live View.

The quick test is 1. focus using Live View. 2. switch of Live View and focus using viewfinder and shutter button. If the lens focus ring moves there is a calibration mismatch.

Re: EOS 6D Mark II Conflicts between viewfinder focusing and Live View focusing

Skip70 — Fri, 18 Apr 2025 20:40:47 GMT

I'm perhaps not explaining well. I'm not talking about focus visible to the eye before shooting (that would be a diopter issue). I'm talking about the actual resultant image. Those should be the same, They are not.

Re: EOS 6D Mark II Conflicts between viewfinder focusing and Live View focusing

Waddizzle — Fri, 18 Apr 2025 20:43:20 GMT

“ The simplest way say this is that the camera is finding a different focus point on the viewfinder method than it is finding using LiveView. While there is always adjustment we can make on a lens, I'm concerned that there is an issue with the camera. “

There is probably nothing wrong with the camera or your lenses. As John pointed out, the camera has separate AF systems for OVF shooting and LV shooting.

This is a result of how DSLRs evolved from film cameras.

The mirror (2) in a film camera redirects the light from the lens (1) upwards to the pentaprism (7), which reflects the light through the viewfinder and to your eye.

A focusing screen (5) served as a manual focusing aid. When the shutter is fired, the mirror swings up to allow the light to reach the film (4).

A DSLR works nearly the same way. The film is replaced by a digital image sensor. The mirror has been redesigned to redirect light both upwards and downwards.

What is not shown in this diagram is the autofocus sensor at the bottom of the mirror box. The AF sensor is precisely located so that the distance from the mirror is equal to the distance from the mirror to the image sensor. An AFMA adjustment calibrates these two distances to be nearly identical. The AF sensor is capable of moving itself to adjust its distance to the mirror.

In Live View shooting mode, the mirror swings up to allow light to reach the image sensor. In this mode of operation, the image sensor is used for auto focusing.

Notice how the distance between the imaging sensor and auto focus sensor will always be identical because they are the same sensor. This also means that you don’t need to calibrate the auto focus, anymore.

Re: EOS 6D Mark II Conflicts between viewfinder focusing and Live View focusing

Skip70 — Fri, 18 Apr 2025 21:11:25 GMT

I might be inviting far too much technical information on this. I appreciated your thorough response and th graphic but I am familiar with the two systems. My simple question remains: When focusing on a point with either the viewfinder or the LiveView the result should be the same Otherwise, we would never know which one to trust is correct.

As far as whether the shared sensor obviates the need for autofocus calibration, I don't see that as true. I have done micro-adjustments on all my lenses, correcting for sometimes subtle, sometimes substantive issues with front or back focus. That's all I was trying to do today until I realized the differential between viewfinder and LiveView. One picture taken with the viewfinder would clearly show front focus; the Live View would show back focus. That suggests to me some issues within the camera.

Re: EOS 6D Mark II Conflicts between viewfinder focusing and Live View focusing

jrhoffman75 — Fri, 18 Apr 2025 21:11:27 GMT

@Skip70 wrote:

I'm perhaps not explaining well. I'm not talking about focus visible to the eye before shooting (that would be a diopter issue). I'm talking about the actual resultant image. Those should be the same, They are not.

https://www.reikanfocal.com/about-autofocus.html

Viewfinder focusing uses a sensor in the bottom of the mirror box. Live View focusing uses the actual sensor that records the image. The camera is calibrated to ensure that when the viewfinder sensor confirms focus the actual image sensor image will be in focus. Sometimes that calibration is off and that is why higher end cameras allow for AFMA (autofocus micro adjustment).
Without you providing sample images it is not possible for us to diagnose your problem.

Re: EOS 6D Mark II Conflicts between viewfinder focusing and Live View focusing

jrhoffman75 — Fri, 18 Apr 2025 21:17:38 GMT

“When focusing on a point with either the viewfinder or the LiveView the result should be the same Otherwise, we would never know which one to trust is correct. ”

This is absolutely true as long as there isn’t a calibration problem. Do you have the focus problem if you are using a Canon lens? You are injecting a second variable by adjusting a third party lens.

Re: EOS 6D Mark II Conflicts between viewfinder focusing and Live View focusing

Skip70 — Fri, 18 Apr 2025 21:26:14 GMT

I am doing micro-adjustment (as I have done for years with all of my lenses) to correct back- or front-focus. In my latest case, when taking a test photo with viewfinder, it showed front focus. When I did exactly the sums photo using Live View, was generally at zero midpoint. (I did provide photos in my original post.)

My simple point is that the viewfinder focus and the Live View focus ought to be the same, otherwise we would never know which one to trust.

Re: EOS 6D Mark II Conflicts between viewfinder focusing and Live View focusing

jrhoffman75 — Fri, 18 Apr 2025 21:34:40 GMT

@Skip70 wrote:

I am doing micro-adjustment (as I have done for years with all of my lenses) to correct back- or front-focus. In my latest case, when taking a test photo with viewfinder, it showed front focus. When I did exactly the sums photo using Live View, was generally at zero midpoint. (I did provide photos in my original post.)

My simple point is that the viewfinder focus and the Live View focus ought to be the same, otherwise we would never know which one to trust.

If Live View and viewfinder focusing results aren’t the same then the camera isn’t calibrated correctly. That is the whole point of AFMA. Something is fundamentally wrong. How are you doing AFMA?

Re: EOS 6D Mark II Conflicts between viewfinder focusing and Live View focusing

Waddizzle — Fri, 18 Apr 2025 22:17:06 GMT

“ That's all I was trying to do today until I realized the differential between viewfinder and LiveView. One picture taken with the viewfinder would clearly show front focus; the Live View would show back focus. That suggests to me some issues within the camera. “

I would suggest clearing the focus settings and retesting before you try to recalibrate. Performing a focus adjustment is not a simple task. It’s far easier to get it wrong than it is to get it right. I have used the Dot Tune Method in the past with excellent results.

Re: EOS 6D Mark II Conflicts between viewfinder focusing and Live View focusing

jrhoffman75 — Fri, 18 Apr 2025 22:23:17 GMT

Ablation (Latin: ablatio – removal) is the removal or destruction of something from an object by vaporization, chipping, erosive processes, or by other means.

😀maybe the camera is attacking the subject.

The photographic term is chromatic aberration. Nothing to do with the topic.

Re: EOS 6D Mark II Conflicts between viewfinder focusing and Live View focusing

Waddizzle — Fri, 18 Apr 2025 22:23:26 GMT

@Skip70 wrote:

Canon 6D Mark II
I am using the Tamron Tap-In console to do micro-focusing on what is now my all stable of Tamron lenses. I am finding a very obvious difference between focus points using the viewfinder and reference focus point using touch screen Live View.

I will try to attach the photos to this post, but the first time using the regular viewfinder focus (spot focus and metering)the focus point) was front focus. I adjusted using the console forward, just as you would with there Canon micro-focus system. However, when I did the same shot zooming in on LiveView, the focus point was clearly back focus, reflecting the influence of my adjustments.

The simplest way say this is that the camera is finding a different focus point on the viewfinder method than it is finding using LiveView. While there is always adjustment we can make on a lens, I'm concerned that there is an issue with the camera.

Ideas?

BTW, are you I using a tripod? Are there images cropped? The framing of your two test shots should be identical. The framing of all your test shots should be identical.

What lenses are you trying to calibarate? Or what lens was used for your posted samples?

Re: EOS 6D Mark II Conflicts between viewfinder focusing and Live View focusing

Skip70 — Fri, 18 Apr 2025 22:49:07 GMT

Thank you, John. You win the boxed set of Occam's Razors. That has been my question and assertion all sling /. Oth images should match. I may have a camera calibration in my future.

Re: EOS 6D Mark II Conflicts between viewfinder focusing and Live View focusing

Skip70 — Fri, 18 Apr 2025 22:54:42 GMT

Of course I dm using a tripod.m Crooping of the final image was just to emphasize the differences and is irrelevant to the issue. I was calibrating a Tdmron SP 35mm 1.4, which has been widely praised for sharpness rivaling first party lenses. Either way, the issue here is not its ability to achieve focus per se but the difference between viewfinder and Live view.

Re: EOS 6D Mark II Conflicts between viewfinder focusing and Live View focusing

jrhoffman75 — Fri, 18 Apr 2025 23:41:55 GMT

@Skip70 wrote:

Thank you, John. You win the boxed set of Occam's Razors. That has been my question and assertion all sling /. Oth images should match. I may have a camera calibration in my future.

Before you do that try using a Canon lens. Separate out the internal calibration issue of the Tamron lens.

Re: EOS 6D Mark II Conflicts between viewfinder focusing and Live View focusing

Skip70 — Fri, 18 Apr 2025 23:53:30 GMT

I have long understood this set-up. What I don't understand is your comment "Notice how the distance between the imaging sensor and the auto focus sensor will always be identical because why are the same sensor." Your diagram depicts that they are not: the image sensor is on the back wall of the divinity, the AF sensor, you said, is below. As well, while we may hope they may be identical. you say earlier that the whole point of AFMA is to adjust until they are. If I understand your point, then, I need to keep adjusting the AFMA until the viewfinder )prism) image matches what is coming off the image sensor (Live View).

Live View, viewfinder and AFMA Sequel

Skip70 — Sat, 19 Apr 2025 09:47:18 GMT

I had so many helpful and expert responses yesterday I admittedly lost track of the line of thinking tracking all those on my iPhone, so get up this morning and carefully read all of them again.

Here is what I take away, a new question , and my action plan:
1. The Life View is not subject to "adjustment" in that it is the actual image projected directly onto the sensor screen. When that's in focus, that will result in a focused image.
2. If, then, an image from the viewfinder system is different, it simply means there is a misalignment or miscalibration in that system. That is what AFMA is designed to address -- making minute physical changes in the alignment of the sensor at the bottom of the mirror box so it matches what would be projected directly onto the image sensor.

The remaining question them, is that role an aftermarket lens calibration system, e.g. Tamron's Tap-In Console has. It is designed to address front and back focus issues, but I'm wondering if it in some way actually may be trying to do the same thing as Canon's AFMA method. If I expand the proposed image in Live View and actually select a focus point on a test card, the final fox point ought to be why I selected, not something in front of or behind that point.