topic Re: 7DMII AF Microadjustment Variation in EOS DSLR & Mirrorless Cameras

7DMII AF Microadjustment Variation

Marc13579 — Tue, 06 Sep 2016 11:08:34 GMT

Hello All,

I was wondering if there is a listed tollerance for variation in AF after applying microadjustment as I'm finding that after I apply micro adjustment, there still seems to be some inconsistencies. In this example I am using my Canon 50mm f1.8. I have set my 7DMII up on a sturdy tripod and have put my Lensalign target with the ruler on another tripod. I measured out the correct distance between the camera body and the target, calibrated the height as the instructions said to do, used the middle AF point, set the camera to "mirror lockup", set the AF drive to One Shot, and using the timer function I took a three test photos to use as a base line at f1.8. Viewing the images on my computer, I discovered that my 50mm f1.8 front focuses a little bit, but not really all that much so I apply a +3 microadjustment, and I go back to my computer to examine the results. Now it back focuses, so I decide to try a +1. I take once picture and examine it on my computer and now the adjustment is right on. That's great, but when I then take a series of test pictures with the +1 adjustment the focal plane varies, and sometimes it varies quite a bit. See these examples:

+1 Correction:

Now front focusing a little bit:

Now back focusing quite a bit:

Now front focusing:

Now front focusing more:

Now back focusing again:

I've had the camera for about a year and in general I shoot a lot of youth and high school sports and mostly at f4.0 so up to now it hasn't made much of difference. But about a month ago a did a short portrait session for a friend, and that's where I discovered the inconsistancy. So ultimatley my question is if there is a "normal" variation in AF or do I need to send my 7DMII in for repair. Thanks for your opinions.

Marc

Re: 7DMII AF Microadjustment Variation

Waddizzle — Tue, 06 Sep 2016 11:51:33 GMT

I assume you are using Dot-Tune. I think you could be seeing the performance limitations of that particular lens.

While it is true, that there can be some variations in the AFMA test results, it usually shows up when performing the same tests under differing lighting conditions, not the same lighting conditions back-to-back. Lighting conditions can significantly affect the test results, which is why Dot-Tune recommends you perform the tests at the shooting location.

Re: 7DMII AF Microadjustment Variation

TTMartin — Tue, 06 Sep 2016 12:01:26 GMT

Are you using the EF 50mm f/1.8 II or the new EF 50mm f/1.8 STM?

The EF 50mm f/1.8 II is a 30 year old lens design and most copies have inconsistent focus. If you are using the EF 50mm f/1.8 II give it to someone you don't like and buy the EF 50mm f/1.8 STM.

Re: 7DMII AF Microadjustment Variation

Marc13579 — Tue, 06 Sep 2016 12:57:54 GMT

"I assume you are using Dot-Tune. I think you could be seeing the performance limitations of that particular lens.

Hi Waddizzle and thanks for the reply.

While I'm not an expert in these things, I was pretty meticulous with my test. Yes, I was using Dot-Tune. I shot all of my calibration images under the same lighting which was under ambient light with a Speedlight set up off camera diffused with a shoot through umbrella to fill out the shadows as best I could. While I thougth it might be a lens issue (these images were shot with the 50mm, f1.8 STM), I actually got similar results calibrating my 24-70 f2.8 II USM and my 70-200 f2.8 II USM. I suppose I should have included those details in the original post.

In the end I've been happy with my 7DMII, but if there is a problem with it naturally I want to have it corrected.

Thanks again...Marc

Re: 7DMII AF Microadjustment Variation

Marc13579 — Tue, 06 Sep 2016 12:59:03 GMT

"Are you using the EF 50mm f/1.8 II or the new EF 50mm f/1.8 STM?"

Hi TT....the STM version. I bought it nine months ago.

Thanks...Marc

Re: 7DMII AF Microadjustment Variation

Waddizzle — Tue, 06 Sep 2016 13:09:59 GMT

What focus mode and shooting mode are you using? When I have made AFMA adjustments, I do them several times under different lighting conditions, and take the average result.

[EDIT] I get the most inconsistent results under artificial lighting, BTW, and the best results in outdoor sunlight.

Re: 7DMII AF Microadjustment Variation

Marc13579 — Tue, 06 Sep 2016 13:14:47 GMT

"What focus mode and shooting mode are you using? When I have made AFMA adjustments, I do them several times under different lighting conditions, and take the average result."

I shot with the drive in One Shot, using single point AF using the center point, mirror lock up, and using a two second timer to make sure that I wasn't inducing any camera shake with my hands.

When you say "...under different lighting conditions, and take the average result", I will admit that I did not consider that. However as you can see I had quite a bit of varying under one lighting condition, so how would one take an average under different conditions?

Or...and this could certainly be a possibility...am I over thinking this?

Marc

Re: 7DMII AF Microadjustment Variation

TTMartin — Tue, 06 Sep 2016 13:54:02 GMT

@Marc13579 wrote:
"What focus mode and shooting mode are you using? When I have made AFMA adjustments, I do them several times under different lighting conditions, and take the average result."

I shot with the drive in One Shot, using single point AF using the center point, mirror lock up, and using a two second timer to make sure that I wasn't inducing any camera shake with my hands.

When you say "...under different lighting conditions, and take the average result", I will admit that I did not consider that. However as you can see I had quite a bit of varying under one lighting condition, so how would one take an average under different conditions?

Or...and this could certainly be a possibility...am I over thinking this?

Marc

First off +1 MFA would not make a noticeably change in the focus.

Of your 6 photos there was only one were the plane of focus wasn't within the depth of field for the lens.

I don't think there is anything wrong with your camera.

I PM'd you a link to an article done by lensrentals.com. They are a great resource, they have many copies of lenses and cameras to work with and Roger Cicala has a good understanding of how the gear works. The link I sent is just one of many articles Roger has done on AF. They are all worth reading.

Re: 7DMII AF Microadjustment Variation

Marc13579 — Tue, 06 Sep 2016 14:25:58 GMT

@TTMartin wrote:
@Marc13579 wrote:
"What focus mode and shooting mode are you using? When I have made AFMA adjustments, I do them several times under different lighting conditions, and take the average result."

I shot with the drive in One Shot, using single point AF using the center point, mirror lock up, and using a two second timer to make sure that I wasn't inducing any camera shake with my hands.

When you say "...under different lighting conditions, and take the average result", I will admit that I did not consider that. However as you can see I had quite a bit of varying under one lighting condition, so how would one take an average under different conditions?

Or...and this could certainly be a possibility...am I over thinking this?

Marc
First off +1 MFA would not make a noticeably change in the focus.

Of your 6 photos there was only one were the plane of focus wasn't within the depth of field for the lens.

I don't think there is anything wrong with your camera.

I PM'd you a link to an article done by lensrentals.com. They are a great resource, they have many copies of lenses and cameras to work with and Roger Cicala has a good understanding of how the gear works. The link I sent is just one of many articles Roger has done on AF. They are all worth reading.

TT,

Firstly I would have thought the MFA of +1 really would not matter. But to the degree that the focus plane was shifting it was puzzling to me how or if I needed to apply more or less.

Secondly the Roger articles are clearing the above up for me. There seems to be a natural variation in focus. He uses the term "pixel peeping"; I would use the term "over thinking". 🙂 The practical position appears to be that regardless of lens/camera combination there will be a small varying of focal plane. If this is the case, then perhaps I will go back to take a few more MFA test shots and see exactly where I am at on an average. Of course this will have to be after the current soccer season (or football, depending on your location).

Thanks much for the guidance!

Marc

Re: 7DMII AF Microadjustment Variation

kvbarkley — Tue, 06 Sep 2016 14:42:04 GMT

I don't know how much engineering you know, but an AF system is a very complicated control loop system involving the camera and the lens. Like all engineered systems it involves tradeoffs in speed and accuracy. Some residual error is not unheard of.

I just had something wierd happen with my T6S. I was just goofing around - I had just shot a close-up of a molting mantis - and when I pointed the camera to a concrete wall very much further away the camera indicated that it had focus when it was obvious *not* in focus. I half pressed several times and got the same indication each time. I finally pointed the camera at something else, achieved focus, and then pointed back to the wall. It focussed just fine. AF is complicated!

Re: 7DMII AF Microadjustment Variation

ScottyP — Tue, 06 Sep 2016 22:16:17 GMT

If you are going to get super picky in the pixel peeping you should probably consider using a more exact calibration method than dot tune, which according to everything I've ever read, is ok for what it is intended to be, which is quick and easy.

Re: 7DMII AF Microadjustment Variation

Marc13579 — Sat, 10 Sep 2016 19:20:09 GMT

All,

Thanks again for the input. Between the comments here and the comments I got in one of the other forums for Canon, I went back and did another MFA with my two "L" series lenses (24-70 f2.8 II and 70-200 f2.8 USM II). I got more consistent results this time. I made a couple of changes to the process that I think helped.

Firstly I pretty much followed everything I did to set up as I originally described in the original post including measuring the correct distance for the focal length, however (Change #1) I put the LensAlign target about four feet in front of a non-white wall as is suggested in the LensAlign directions. I'm not sure if this really makes any difference, but I can sort of see how it might so I did it. Since three of the four walls of the room were white as so was the ceiling I then used an off camera Speedlight pointed straight up (Change #2) to evenly light the target instead of a shoot through umbrella and used ETTL. I shot in I shot in "One Shot" with the center point as my focus point, used mirror lock up, a two second timer, a shutter speed of 1/500 and at f2.8 with an ISO of 400 for everything. I begin with 0 correction, of course. So there is the set up.

With the 24-70 I started with 70mm and took a series of five photos. However before I take each photo (change #3...and what I think really made the difference) I manually rotated the focus ring completely in one direction so that the focusing mechanism had to fully travel to achieve proper focus. When I examined the images in Lightroom at 100 percent, I found that four of five images showed about the same amount of front focus. The fifth image showed a significantly different amount of front focus. I reasoned that I could discard this image as an outlier and relied on the data from the other four. I went back and repeated the same process for each amount of MFA that I chose, discarding any single outlier. At the end I shot 10 images and found that I got acceptably consistent results (my non-scientific definition to mean “I’m good with that”) in 9 of 10 images. I repeated the entire process for 24mm with the same result.

For the 70-200 I did essentially the same thing, however (change #4) I made sure to have the distance limiter set to 1.2 meters. In the series of 10 images I would only get between 7 and 8 images that were “acceptably consistent” (yes, I repeated the sequence a few times). So I can conclude that with my 70-200 there is either some variation in the lens that prevents more consistent results or that the camera/lens combination is preventing better results. Since my lens is four years old and it gets a lot of use, I am leaning towards the lens being in need of some servicing.

I haven't recalibrated my 50mm 1.8 STM yet as I just ran out of time.

Just for fun I tried manually focusing both lenses using Live View, and I ended up with the same focal plane as the AF system.

Anyway, I figured that since I discovered better results I would be sure to follow up here. Thanks for your comments.

Marc

Re: 7DMII AF Microadjustment Variation

TTMartin — Fri, 09 Sep 2016 19:00:36 GMT

Thanks for the follow up post and sharing the tips you used to get better results.