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Author Topic: Are autofocus issues common for everyone? *UPDATED*  (Read 6797 times)

nightbreath

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Are autofocus issues common for everyone? *UPDATED*
« on: February 11, 2012, 05:07:34 PM »
I have a Canon 7D and few lenses. The issue I’m experiencing for more than 2 years is related to autofocus with fast primes and can be replicated when camera is focusing at a non-contrast area. It doesn't matter what type of focusing / focusing point I use – I hear focus confirmation in the same manner as if camera has focused properly, but when I make the shot I see that it didn’t.

I've run several tests and identified that the lens AF is inconsistent comparing to Live View autofocus, when area in focus has no contrast. When I use lens AF in ~80% shots I'm getting front-focus issue.

Attached are crops from my tests, red square is the focusing point. Could someone confirm that this is normal behavior? Or should I sent my camera to Canon?

P.S. Shots were taken at ISO 800, 1/80 of a second, f/1.2 and f/1.4, using tripod.
« Last Edit: February 12, 2012, 11:49:21 AM by nightbreath »
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Are autofocus issues common for everyone? *UPDATED*
« on: February 11, 2012, 05:07:34 PM »

smirkypants

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Re: Are autofocus issues common for everyone?
« Reply #1 on: February 11, 2012, 05:14:23 PM »
What kind of lens are you using? Have you micro-adjusted it?

neuroanatomist

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Re: Are autofocus issues common for everyone?
« Reply #2 on: February 11, 2012, 05:55:51 PM »
What kind of lens are you using? Have you micro-adjusted it?

I'll see those questions, a raise you what AF mode (one shot or AI focus) and have you changed any AF tracking defaults, and if so, which and to what settings?
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neuroanatomist

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Re: Are autofocus issues common for everyone?
« Reply #3 on: February 11, 2012, 06:16:17 PM »
Also, what aperture, and did you focus/recompose?
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Kernuak

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Re: Are autofocus issues common for everyone?
« Reply #4 on: February 12, 2012, 05:40:21 AM »
Which focus mode are you using? Spot, Single point, expanded, zone or all points? Also have you adjusted the tracking sensitivity or is it still at the default setting. The focus modes on the 7D are much more complex than other consumer and semi-pro cameras and it is only the 1D/1Ds series that are more complex. If you don't use the best mode for the job, then it can be erratic, so we need to rule that out as a cause first.
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te4o

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Re: Are autofocus issues common for everyone?
« Reply #5 on: February 12, 2012, 06:07:18 AM »
Focus shift ? Very common with fast lenses if stopped down. 50/1.4 has some of it. Almost all 50s/1.4 and less have it.
Just an idea. I am probably wrong as I just read about it but I am not a tech spec.
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briansquibb

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Re: Are autofocus issues common for everyone?
« Reply #6 on: February 12, 2012, 06:11:33 AM »
Which focus mode are you using? Spot, Single point, expanded, zone or all points? Also have you adjusted the tracking sensitivity or is it still at the default setting. The focus modes on the 7D are much more complex than other consumer and semi-pro cameras and it is only the 1D/1Ds series that are more complex. If you don't use the best mode for the job, then it can be erratic, so we need to rule that out as a cause first.

I dont believe they are more complex - just more points to choose from - that includes the 1D series as well

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Re: Are autofocus issues common for everyone?
« Reply #6 on: February 12, 2012, 06:11:33 AM »

Kernuak

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Re: Are autofocus issues common for everyone?
« Reply #7 on: February 12, 2012, 07:40:28 AM »
I don't use AF much with my 50mm f/1.4, so I don't have any direct comparisons. However, I have read of issues with the 50mm AF being erratic at times. You are always going to have a greater risk of focusing issues with low contrast subjects, simply because the AF uses the contrast to make the decision on where to focus, however, it will only focus within the area of the active focus point(s), so any high contrast areas away from the focus point will be irrelevant. I once did a test using the 7D and 50mm f/1.4 at night with street lighting against my white garage door and surrounding brick work. I found that the focusing accuracy varied according to the ISO setting chosen, although it wasn't really a proper test (I was handholding for a start), so I could have been mistaken. If you only sent the lens for calibration without the body, then they won't necessarily be matched, so you could try microadjustment, but I would rule out othe causes first, in case it makes it worse. Try a similar subject in different lighting and two different subjects with different contrast levels in the same place, to see if it makes a difference. If it does, then MA is unlikely to help.
In your first example at the wedding, it's difficult to say for sure if the leaves are in front or behind the people, also, from the little of her chin visible in the crop, it looks like it may be in sharper focus than her chest, so that could be due to focus and recompose if you were using the lens wide open, as the focal plane would be changing. When you focus while pointing the camera up or down, then hold it level, it will have the same type of effect as using a tilt and shift lens, where even one degree of tilt can make a difference (although you can't compare one degree of camera tilt to one degree of a TSE lens tilt).
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Kernuak

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Re: Are autofocus issues common for everyone?
« Reply #8 on: February 12, 2012, 07:50:40 AM »
Which focus mode are you using? Spot, Single point, expanded, zone or all points? Also have you adjusted the tracking sensitivity or is it still at the default setting. The focus modes on the 7D are much more complex than other consumer and semi-pro cameras and it is only the 1D/1Ds series that are more complex. If you don't use the best mode for the job, then it can be erratic, so we need to rule that out as a cause first.

I dont believe they are more complex - just more points to choose from - that includes the 1D series as well
The simple fact that there are more points to choose from means it is more complex, after all, many people never change from the central point. But beyond that, there are a lot more focus modes to choose from and choosing the wrong one can change the behaviour and cause focusing errors. Many who aren't aware of the complexities, may simply choose the default of all points and find that it focuses on the nose of a person, instead of their eyes, they may then think that the camera AF isn't working properly. In comparison, if they had used the spot focus mode and chose an off centre point, then they could have had the eyes correctly in focus. It's the same with wildlife, you either get the wing tip (potentially) or the head. It's fine if you understand that, as most on here do, but many using the 7D for the first time (especially if it also happens to be their first camera), may not be aware of that. Whenever you increase versatility, there is always the chance of increased complexity.
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briansquibb

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Re: Are autofocus issues common for everyone?
« Reply #9 on: February 12, 2012, 08:52:58 AM »
Which focus mode are you using? Spot, Single point, expanded, zone or all points? Also have you adjusted the tracking sensitivity or is it still at the default setting. The focus modes on the 7D are much more complex than other consumer and semi-pro cameras and it is only the 1D/1Ds series that are more complex. If you don't use the best mode for the job, then it can be erratic, so we need to rule that out as a cause first.

I dont believe they are more complex - just more points to choose from - that includes the 1D series as well
The simple fact that there are more points to choose from means it is more complex, after all, many people never change from the central point. But beyond that, there are a lot more focus modes to choose from and choosing the wrong one can change the behaviour and cause focusing errors. Many who aren't aware of the complexities, may simply choose the default of all points and find that it focuses on the nose of a person, instead of their eyes, they may then think that the camera AF isn't working properly. In comparison, if they had used the spot focus mode and chose an off centre point, then they could have had the eyes correctly in focus. It's the same with wildlife, you either get the wing tip (potentially) or the head. It's fine if you understand that, as most on here do, but many using the 7D for the first time (especially if it also happens to be their first camera), may not be aware of that. Whenever you increase versatility, there is always the chance of increased complexity.

To me the complexity is the same for all the current digitals - you move the focus point to the right place and take the picture.

The only differences comes when you get the configuration options such as expansion points and tracking sensitivity.

Operator ignorance is nothing to do with the camera - whether there are 9 points, 19 points or 41 point is just giving the user finer granularity.


Kernuak

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Re: Are autofocus issues common for everyone?
« Reply #10 on: February 12, 2012, 09:48:15 AM »
Which focus mode are you using? Spot, Single point, expanded, zone or all points? Also have you adjusted the tracking sensitivity or is it still at the default setting. The focus modes on the 7D are much more complex than other consumer and semi-pro cameras and it is only the 1D/1Ds series that are more complex. If you don't use the best mode for the job, then it can be erratic, so we need to rule that out as a cause first.

I dont believe they are more complex - just more points to choose from - that includes the 1D series as well
The simple fact that there are more points to choose from means it is more complex, after all, many people never change from the central point. But beyond that, there are a lot more focus modes to choose from and choosing the wrong one can change the behaviour and cause focusing errors. Many who aren't aware of the complexities, may simply choose the default of all points and find that it focuses on the nose of a person, instead of their eyes, they may then think that the camera AF isn't working properly. In comparison, if they had used the spot focus mode and chose an off centre point, then they could have had the eyes correctly in focus. It's the same with wildlife, you either get the wing tip (potentially) or the head. It's fine if you understand that, as most on here do, but many using the 7D for the first time (especially if it also happens to be their first camera), may not be aware of that. Whenever you increase versatility, there is always the chance of increased complexity.

To me the complexity is the same for all the current digitals - you move the focus point to the right place and take the picture.

The only differences comes when you get the configuration options such as expansion points and tracking sensitivity.

Operator ignorance is nothing to do with the camera - whether there are 9 points, 19 points or 41 point is just giving the user finer granularity.
Granted, but if you take it to the extreme, a system with only a single point would mean you wouldn't have to change at all. The choices you would have to make are simpler, you simply have to make a choice on what depth of field you want and what composition, you wouldn't need to worry about focusing at all, as you'd get what you were given. By definition, any system that gives you more options is more complex. Whether or not any one individual finds it complicated will depend on their prior experience and their ability to adapt to the greater degree of choice. For some people, the 7D system is stil relatively simple, while for others, it is more than they can cope with (either in reality or because they can't or don't want to take the time to learn it).
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Re: Are autofocus issues common for everyone?
« Reply #11 on: February 12, 2012, 11:05:15 AM »
Very interesting! I just bought the FoCal software to set MicroAdjustment on all my lenses on the 7D and 5DMkII. The 50 1.4 set up just fine on the 5D2 and there was a fairly drastic improvement. It wouldn't set up at all on the 7D!! Recommended point was way out of focus, and no matter what settings I resorted to it simply would not focus for the test. So, I tried to manually set the MA using Live View...no longer hooked up to the computer at all....and the 50 1.4 simply would not focus with LiveView!! I could manually adjust it for a nice sharp image and then hit the focus button in Live View and it would run out! After testing it manually to see where standard af was placing focus, I MA to -3 and it looked pretty good. Click Live View on and set focus and bam, way out again! I have no clue why the 50 1.4 won't focus in live view on my 7D but there it is...

briansquibb

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Re: Are autofocus issues common for everyone?
« Reply #12 on: February 12, 2012, 11:15:16 AM »

Granted, but if you take it to the extreme, a system with only a single point would mean you wouldn't have to change at all. The choices you would have to make are simpler, you simply have to make a choice on what depth of field you want and what composition, you wouldn't need to worry about focusing at all, as you'd get what you were given. By definition, any system that gives you more options is more complex. Whether or not any one individual finds it complicated will depend on their prior experience and their ability to adapt to the greater degree of choice. For some people, the 7D system is stil relatively simple, while for others, it is more than they can cope with (either in reality or because they can't or don't want to take the time to learn it).

Here is an example of that from this morning.

550 pictures taken:

     - all in portrait
     - all with focus point 1 up from centre
     - all 1/500, f/5.6
     - all with auto iso (varied from 100 to 200)
     - focus mode - AI Servo

Just made the settings and it became a point and shoot :D

1D4 + 70-200II
« Last Edit: February 12, 2012, 11:27:20 AM by briansquibb »

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Re: Are autofocus issues common for everyone?
« Reply #12 on: February 12, 2012, 11:15:16 AM »

nightbreath

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Re: Are autofocus issues common for everyone? *UPDATED*
« Reply #13 on: February 12, 2012, 11:46:32 AM »
Thank you for your responses. I've run more tests and identified the problem.

I have updated my first message, so the latest information can be found there. Could you please look at it and leave a comment?
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neuroanatomist

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Re: Are autofocus issues common for everyone? *UPDATED*
« Reply #14 on: February 12, 2012, 12:04:20 PM »
I've run several tests and identified that the lens AF is inconsistent comparing to Live View autofocus, when area in focus has no contrast. When I use lens AF in ~80% shots I'm getting front-focus issue.

Attached are crops from my tests, red square is the focusing point. Could someone confirm that this is normal behavior? Or should I sent my camera to Canon?

Let me ask again, with emphasis. Have you done an AF microadjustment??
EOS 1D X, EOS M, and lots of lenses
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Re: Are autofocus issues common for everyone? *UPDATED*
« Reply #14 on: February 12, 2012, 12:04:20 PM »