6D focus issues

Hello fellow POTNers,

I think I have focus issue with my 6D and fast primes. I previously only had a 24-105 f4L and 85mm 1.8, and a Sigma 35 joined the family for Xmas.

I have been trying to calibrate my lenses so they work perfectly but it seems I can never reach a satisfying value (I also test with a 50mm 1.8): for each lense, I manage to dial a satisfying value which works for each distance. Then after some times...it does not work anymore, which is getting quite annoying.

It seems it varies between three values: 0, +6 and +14.

Also, outer focus points seems not to work wide open...

Has anyone experienced this issue? How could it be explaines? Faulty AF sensors? Could Canon fix it?

Thanks for your help!

jermeietard

First of all post or link to a poor image that has the full EXIF information. That enables us to see virtually every setting of the camera and thus more likely avoid speculation as to cause.

It's been noted that the AF of the 50/1.8 is too erratic to reliably Micro Focus it. I've seen discussion of that various places. Reikan FoCal, which runs a series of focus tests to establish a useful amount of adjustment, gave up on the EF 50/1.8, because it was so erratic that any correction dialed in was meaningless.

But your other lenses should be "fine tunable".

The 6D's center AF point is the only cross-type in the array and is much better than the other 10 peripheral points. The center one is rated by Canon to -3EV, while the all the others are only rated to be able to focus down to +0.5EV. So be sure you are doing your testing in really good light. (For comparison, the 5D Mark III has 61 points, upt to 41 of which are cross-type, and is rated to -2EV with all of those).

I don't know why the MFA settings you are making aren't being retained. Are you losing other settings in the menu or custom functions? If so, I'd suspect the memory battery (which unfortunately isn't user replaceable).

Thanks to the both of you for your help!

John from PA wrote in post #16577365
First of all post or link to a poor image that has the full EXIF information. That enables us to see virtually every setting of the camera and thus more likely avoid speculation as to cause.

I've formatted my SD card and it's now night time in France, I will post some examples tomorrow

amfoto1 wrote in post #16577393
It's been noted that the AF of the 50/1.8 is too erratic to reliably Micro Focus it. I've seen discussion of that various places. Reikan FoCal, which runs a series of focus tests to establish a useful amount of adjustment, gave up on the EF 50/1.8, because it was so erratic that any correction dialed in was meaningless.

But your other lenses should be "fine tunable".

The 6D's center AF point is the only cross-type in the array and is much better than the other 10 peripheral points. The center one is rated by Canon to -3EV, while the all the others are only rated to be able to focus down to +0.5EV. So be sure you are doing your testing in really good light. (For comparison, the 5D Mark III has 61 points, upt to 41 of which are cross-type, and is rated to -2EV with all of those).

I don't know why the MFA settings you are making aren't being retained. Are you losing other settings in the menu or custom functions? If so, I'd suspect the memory battery (which unfortunately isn't user replaceable).

I was aware of the type of sensors difference in 6D between the center point and the outer ones; but this is something I seem to be able to fix with MFA so I was thinking they were not getting the proper information. But well if I can get the center point working properly that would be great

I don't know if the settings are not retained, they are still displayed in the menu, but for a period of times all my pictures will be perfect with a +14 dialed, then for another period of time it will be perfect with a 0... Really strange!

There's also another strange thing, not matter the MFA setting I cannot manage to get the iris' sharp, but the eye lashes are razor sharp.

But I think it will be clearer with the pictures tomorrow! Thanks again for your help!

As promised, here is a dropbox folder including a few pictures : https://www.dropbox.co​m/sh/a2fv7398xjrkz2v/L​1NodbhENQ (all five files should be available in a couple of minutes). Files include all exif data and if you open them with DPP you'll be able to see the focus points used.

In the 35mm folder :

9925 : AFMA +14, razor sharp

Then a couple minutes later after removing lens and re attaching it, +14 is OoF (9967) and 0 is ok (9968).

In the 85mm folder :

This is the best example I could find for the 85mm and I know it was quite dqrk but I expect the lense to work properly in such conditions.

9909 : AFMA = +8 → bad AF
9910 : AFMA = 0 OK

I’ve had the 85mm for four month and traveled with it. Sometimes it did not focus properly but MFA = 0 provided the best result. Now it seems =8 yields the best results…strange!

Edit: I've also added an "eyes" foler: This is an example of me not being able to get a tack sharp iris. Am I having unrealistic expectations or should I be able to get better results?

I went around the MFA merry go round and it's not always a fun trip.

I had a 50 1.4 that was erratic when shot at or near wide open. MFA was +13 or so to even get close but the inconsistency led me to return for refund.

Unlike some others, I'm getting great performance out of my 50 1.8. Strange, but there you go.

Also, my MFA technique was poor, which can easily lead to getting wrong or different settings. Once the camera is set wrong, real world results will be irratic and disappointing.

A few things:

Only MFA in great light and not the long tube fluorescent type of lights. Avoid low or marginal light. Focus will be less precise and consistent in challenging light and MFA will not fix this. It is a different issue, so MFA in great light and then see what the issues are in poorer light.

Avoid setting MFA at close distances. It is more convenient and easier to see results due to razor thin DOF at closer distances, but unless you always shoot at those distances your MFA will likely be off. The usual guide is 50x the focal length. And MFA wide open at sufficient shutter speed to avoid motion/vibration blur and use a tripod with IS off.

Beware what target you use. The focus sensor is larger than the little red box so it's easy, if using a slanted target, to have the camera focus closer than where you think it should. This is also good to know as it can throw off focus on real world targets (nose instead of eyes etc.).

Others can chime in with other advice or links to better posts/threads on the topic.

Almost forgot, the 24-105 has a reputation as being a very fast and accurate focusing lens. Your others may deviate in varying amounts from its high standard.

Thanks for you reply Gobeaty!

As the light is really bad at this time of year I've tested under halogen lighting (read somewhere it was a good light for AFMA tests), but you're right maybe I could change target. You're saying the Af sensors are bigger than the square? Sometimes I am trying to figure out exactly where the contrast detection is achieved and I even wonder if it's not outside the box.

I can confirm the 24-105 is really great as far as focus is concerned!

jeremietard wrote in post #16577258
Hello fellow POTNers,

I think I have focus issue with my 6D and fast primes. I previously only had a 24-105 f4L and 85mm 1.8, and a Sigma 35 joined the family for Xmas.

I have been trying to calibrate my lenses so they work perfectly but it seems I can never reach a satisfying value (I also test with a 50mm 1.8): for each lense, I manage to dial a satisfying value which works for each distance. Then after some times...it does not work anymore, which is getting quite annoying.

It seems it varies between three values: 0, +6 and +14.

Also, outer focus points seems not to work wide open...

Has anyone experienced this issue? How could it be explaines? Faulty AF sensors? Could Canon fix it?

Thanks for your help!

jermeietard

I found my experience of microadjusting some lenses were very inconsistent although were otherwise very good lenses, examples are the 50/1.4 and very surprisingly the 100 macro. The 24-105 and most other lenses were fine.

This sort of behaviour was exacerbated when the test distance was short, Canon recommend 50X the focal length from memory, with these lenses I have problems at ~22X the focal length distance.

Try testing as close as you can get to 50X the focal length. Take test shots with new AF operations at least three times for each MA setting, AF can vary from shot to shot. Try stepping through the MA range in steps of 5 at a time.

I am glad to learn I am not the only one having problem MFAing my lenses!

How did you solve your issue at 22x the FL?

Has anyone been able to have the issue fixed by Canon?

For problem lenses just work at 50x focal length as Canon recommends.

This is so frustrating!

I think I am going to buy FoCal plus and see if it can solve my problems!

Shoot outdoors with good light. Recommended to MFA in the condition you are usually shooting in. Try distant trees with fine leaves.

Zoom lenses, there are at least 2 MFA to reckon with. One at the wide end, and the other at the long end. The right "setting" will be in between.

Light, temperature, moisture will all affect and vary lens MFA settings. And they will change, if you move from one extreme to another.

Living in apartment it's difficult to test outside (and even harder when days are quite dark as today).

I purchased Focal (in its plus version) and will test it tonite with an halogen light direct to the target. Then during the week end I will try to test it outside to see it it makes a difference.

jeremietard wrote in post #16581812
Living in apartment it's difficult to test outside (and even harder when days are quite dark as today).

I purchased Focal (in its plus version) and will test it tonite with an halogen light direct to the target. Then during the week end I will try to test it outside to see it it makes a difference.

Ok. Good luck and looking forward to your updates.

Thanks! I hope I'll soon be able to tell you it's fixed!