Canon's ability to fix AF?

Hello everyone,

With the three fast prime I own with my 6D (Canon 50 and 85 in 1.8 versions ; Sigma 35mm 1,4) focus is spot on using the central focus point, and the farther you are from the center and the more front focused the image is. This is not a sensitivy issue (cross type vs non cross type) as focus can be achieved perfectly with a different MFA value per AF sensor.

I do not have a Canon service center and have the possibility to drop my 6D at a service center on march 16th, and need it back before the end of the first week of april. I cannot drop it later as my body will not be under warranty anymore.

Canon service center guys are not very talkative and I have not had the confirmation whether their tools allows them to fix this kind of issue. Otherwise and I will not bother dropping my 6D to them and will stick with focus and recompose even if it is not ideal.

I would like to know if Canon can enter some kind of offset for each AF points to make sure all sensors are working as designed.

Thanks!

jeremietard

I think they can but I'm going to follow this because I'm interested. When you think about it anything can be fixed. I can't speak for all Canon facilities. I know Canon USA does a very good job.

This is interesting. I'd also like to know. I would assume they could.

I've sent them my phone number hoping they'll contact me on Monday. I'll keep you posted if they can make this fix

I've finally been able to talk to a Canon technician today. Apparently they do not have any tool (soft or hardware) which allows to set each focus points independently.

They can however check the AF system for any issue but he says it's not likely to fix the issue...

I have retested each focus points tonite and it seems the outer left one has trouble locking into subjets so I think I will send my body to them for checks

Check during the day in good daylight. It is amazing how many hidden issues crop up at night, especially with CFL lights.

Also, does the symmetric point (from the center) have the same or opposite problem?

Say if the leftmost point needs -15 MFA does the rightmost point need +15 or +10 or some + number?

I am looking whether the box is misaligned...

They don't usually tell you much before you send it in. However, when I have used the Irvine center in CA, they have been very good, even with stuff under warranty (i.e. it doesn't seem like they skimp just because because it is under warranty).

You never know what they might find even with standard tests. Those tests might show up a problem somewhere that is not obviously directly related to your issue and they will just change out that part. Since your reset changed something, it maybe be an electronics issue that they can find and put in a new part.

MakisM1 wrote in post #16742009
Check during the day in good daylight. It is amazing how many hidden issues crop up at night, especially with CFL lights.

Also, does the symmetric point (from the center) have the same or opposite problem?

Say if the leftmost point needs -15 MFA does the rightmost point need +15 or +10 or some + number?

I am looking whether the box is misaligned...

I have re-checked today and though the accuracy with the outer focus points I feel they all front focus; but you're right I will have Canon check the sensor alignment. The fare left focus point is REALLY bad, I performed a test with the 24-105 f4L, focused on an object on a table and the focus was on an object 1,5m in front! Nowhere near usable!!

ejenner wrote in post #16742524
They don't usually tell you much before you send it in. However, when I have used the Irvine center in CA, they have been very good, even with stuff under warranty (i.e. it doesn't seem like they skimp just because because it is under warranty).

You never know what they might find even with standard tests. Those tests might show up a problem somewhere that is not obviously directly related to your issue and they will just change out that part. Since your reset changed something, it maybe be an electronics issue that they can find and put in a new part.

Yes you're probably right, they may correct a bunch of things and the combination of thes ethings may solve my issue

Got a call from the Canon technician servicing my 6D today. He said the malfunctioning focus point was because of dust spot stuck on the miror (the small one below the big one) and which was masking the AF sensor. Should get my camera back in the middle of newt week

jeremietard wrote in post #16756275
Got a call from the Canon technician servicing my 6D today. He said the malfunctioning focus point was because of dust spot stuck on the miror (the small one below the big one) and which was masking the AF sensor. Should get my camera back in the middle of newt week

That's good news!

Just got my 6D back from the service center. As the technician explained before sending the body in they do not have any tool to fix the front focus with outer points ; but they fixed the one which did not work so I'm happy

jeremietard wrote in post #16770659
Just got my 6D back from the service center. As the technician explained before sending the body in they do not have any tool to fix the front focus with outer points ; but they fixed the one which did not work so I'm happy

How do you know if your lens is not decentered or more likely has field curvature in its design? What makes you suspect its the camera body and not the nature of that specific lens? It is very common for even top quality lenses like the Canon 17 TSE to have some field curvature, where the edges (ie L/R in landscape orientation) of the image are somewhat front focused relative to the image center. Most lenses outside of macro are not perfectly flat field focus.
Mike K

Well I can't really know. Even with field curvature I expected the camera to be able to reach a good focus. Maybe it's just not possible but I think this weird. If I had not had the issue of the non-working focus point (which ended up being due to a stuck piece of dust on the AF mirror) I would not have sent it back ; I will only use the central af point at wide apertures

Just a thought but I would have ask the tech if he could of adjusted the center point to the average of the outer points, then your mfa would help all the points

Mike K wrote in post #16770924
How do you know if your lens is not decentered or more likely has field curvature in its design? What makes you suspect its the camera body and not the nature of that specific lens? It is very common for even top quality lenses like the Canon 17 TSE to have some field curvature, where the edges (ie L/R in landscape orientation) of the image are somewhat front focused relative to the image center. Most lenses outside of macro are not perfectly flat field focus.
Mike K

The camera has a database of Canon lenses, to allow it to know the field curvature of the different lenses and adapt the off-center focus points accordingly.

That is one thing that makes life harder for third-part lens manufacturers.