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X-T2 AutoFocus very erratic on fine structures (trees)

AF Autofocus X-T2 sharpness focus blurry

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#1 huck222

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Posted 11 March 2017 - 10:21 PM

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the XT-2 Autofocus seems to have severe issues with certain fine structures. Just spent many frustrating hours:

I was actually testing lenses on what i thought makes a perfect object: fine twigs against the sky. Set it on a tripod, with the 10-24. The AF is very inaccurate or erratic, at 24 mm i get many blurry images. Same with the super sharp 35/f2, but smaller differences. (No problems with the 56, thats perfect). Also tested it on the X-T1, kind of the same issues.

I might have it repaired/exchanged, and HOPE there's a fix. I'm wondering if maybe the AF System can not "see" fine structures, like fine branches. But it's high contrast against the sky (the rather poor AF on my old Canon 5D2 and 6D never had problems like this). That would mean serious problems with landscape photography...i mean, it's just a usual object. Nothing extreme or difficult for AF. Attached a 100% crop: image to the right is sharp, shot right after the blurry one. I got tons of that erratic sharpness.

New firmware, all 135 AF points activated. Single point focus.

Looking forward to your opinions/experiences...thanks!

Attached Files


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#2 CDBC

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Posted 12 March 2017 - 08:21 AM

Why is this a problem for you?

 

Any photographer who understands depth of field - and, if necessary, how to use aperture priority if shooting in automatic - would be able to get around this issue.

 

Your camera is a tool; learn how to use it.


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#3 huck222

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Posted 12 March 2017 - 08:50 AM

Why is this a problem for you?

 

Any photographer who understands depth of field - and, if necessary, how to use aperture priority if shooting in automatic - would be able to get around this issue.

 

Your camera is a tool; learn how to use it.

Oh my goodness, here we go. Listen Mr. smart, i do understand depth of field and all. But. This question is about AF accuracy. Why is there AF anyway? If i point my camera at a tree, then the AF should just do it's job, and focus on that tree. Right? Because it is a tool. Why do you think i was in automatic mode? I was in manual. By the way, on many many shots in this series, f5,6 was way softer than f/4. Also had soft images with stopped down apertures. So again, this is about AF acurracy. And you know, sometimes we use an open aperture. And i'm used to AF tools that just focus on that focus point.


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#4 huck222

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Posted 12 March 2017 - 08:53 AM

here's another sample. f5,6 softer than f4. very contrasty object again, i would say.

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#5 huck222

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Posted 12 March 2017 - 08:59 AM

...and just to get that DOF thing out of the way, those trees are about 80 meters/yards away, so at that focal lenght DOF is not a point really.



#6 kimcarsons

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Posted 12 March 2017 - 09:23 AM

here's another sample. f5,6 softer than f4. very contrasty object again, i would say.

 

Could be camera shake there, since you've got a slower shutter speed at F/5.6. It's hard to tell if it's out of focus without seeing something in the frame that *is* in focus. Not saying I don't believe you...



#7 kimcarsons

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Posted 12 March 2017 - 09:24 AM

...and just to get that DOF thing out of the way, those trees are about 80 meters/yards away, so at that focal lenght DOF is not a point really.

 

Actually, it can be. These lenses can focus past infinity, in which case everything will appear out of focus, even with a small aperture.



#8 huck222

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Posted 12 March 2017 - 09:45 AM

Could be camera shake there, since you've got a slower shutter speed at F/5.6. It's hard to tell if it's out of focus without seeing something in the frame that *is* in focus. Not saying I don't believe you...

well i think at 35 mm 1/250s can be no shake. And then you usually can see some lets call ist "directional moving blurriness" =)



#9 huck222

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Posted 12 March 2017 - 09:48 AM

Actually, it can be. These lenses can focus past infinity, in which case everything will appear out of focus, even with a small aperture.

Okay, but as you said "everything will appear out of focus, even with a small aperture." So, a small aperture is no fix here. And should not be required to compensate for AF inacurracy.


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#10 kimcarsons

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Posted 12 March 2017 - 09:50 AM

well i think at 35 mm 1/250s can be no shake. And then you usually can see some lets call ist "directional moving blurriness" =)

 

It all depends on how much the camera is shaking and how close you zoom in to examine the picture. The reciprocal rule is from the film days. I'm just saying if you want to provide an example of the problem, it would be best to use the same shutter speed in both shots, and preferably a more three dimensional scene so if the focus was missed we can see where it landed. 

 

It would also help to see the entire shot, because if there's any backlight in it then that will definitely contribute to AF failures.



#11 kimcarsons

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Posted 12 March 2017 - 09:52 AM

Okay, but as you said "everything will appear out of focus, even with a small aperture." So, a small aperture is no fix here. And should not be required to compensate for AF inacurracy.

 

I agree with you that one shouldn't have to compensate for AF inaccuracy. I'm just saying that even shooting at f/16 does not guarantee and in-focus image. If the lens focuses past infinity (which is likely with AF failure for subjects at this distance), then the shot will be a little out of focus even at the smallest/sharpest aperture. 



#12 milandro

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Posted 12 March 2017 - 10:10 AM

these blurred pictures might ( even at 250) be the fruit of motion blur or there is something wrong about this camera somewhere.

 

I recently bought a 16-55 and shot several pictures (on X-T1) which were not as sharp as they should have been. Turns out that the aperture of this lens didn’t close at the chosen value straight away, it looked like it was doing this in slow motion and if you quickly shot ( it might have taken a second to completely close) there were lot of shots out of focus.

 

I returned the lens and decided anyway that it was too big and heavy for me.


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the popular expression wishful thinking is an oxymoron!

 

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#13 huck222

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Posted 13 March 2017 - 04:02 PM

I agree with you that one shouldn't have to compensate for AF inaccuracy. I'm just saying that even shooting at f/16 does not guarantee and in-focus image. If the lens focuses past infinity (which is likely with AF failure for subjects at this distance), then the shot will be a little out of focus even at the smallest/sharpest aperture. 

Fine. So we both agree, that DOF is not the point. The question then arises, WHY would the camera focus past infinity? That's the point here. Why does the AF not focus correctly? Are fine structures a probelm for this type of AF? Spent yesterday with "easier" subjects, and got less blurrs. But still, some glitches.



#14 kimcarsons

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Posted 13 March 2017 - 05:13 PM

Fine. So we both agree, that DOF is not the point. The question then arises, WHY would the camera focus past infinity? That's the point here. Why does the AF not focus correctly? Are fine structures a probelm for this type of AF? Spent yesterday with "easier" subjects, and got less blurrs. But still, some glitches.

 

I don't know of any particular problems with "fine structures." The phase detect AF system is only sensitive to vertical lines, though, so subject lacking in those will result in AF failure. I think your example my be failing because of backlight in the shot, which will also cause AF failures. There are many ways to make the AF system fail. In order to figure out if you've discovered a new one, you're going to have to go about it scientifically.

 

Of course, it could also be a problem with the lens... Just recently Fuji released a firmware update to the 18-135mm lens to fix erratic AF at the long end, and the 18-55mm had OIS vibrations at the long end for years before the firmware fix came out. 



#15 huck222

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Posted 13 March 2017 - 05:22 PM

Oh ok, didnt know PhAF is only sensitive to vertical lines. Its not like Fuji would specify that =).

Regarding Backlight, No really, really there was no backlight whatsoever.



#16 kimcarsons

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Posted 13 March 2017 - 05:35 PM

Oh ok, didnt know PhAF is only sensitive to vertical lines. Its not like Fuji would specify that =).

Regarding Backlight, No really, really there was no backlight whatsoever.

 

I think those tree branches against the sky qualify as backlight... I haven't personally tried to focus on such a subject with the X-T2 because even from DLSR days I would have low expectations of a good result from such a subject. 



#17 Gibeon

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Posted 14 March 2017 - 03:53 AM

The only thing I can think of is that you might have "Focus/Release Priority" set to release rather than focus. This would let the camera take pictures that are not actually in focus regardless of AF setting.

 

It is in the "AF MF" menu on the second page (on my X-T20) and the default when the camera was just out-of-the-box was set to release. I haven't had any problems with the 56 or the 55-200, or manually focusing my Nikon lenses.

 

Otherwise, if it isn't that, then maybe you're in AF-C? 



#18 huck222

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Posted 14 March 2017 - 06:57 AM

thanks, no, it's focus priority and AF-S, not C.

even otherwise, the AF should focus correctly in this very static setting.



#19 mdm

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Posted 14 March 2017 - 09:57 AM

The second example with the building looks like AF system malfunction. When in preview mode you press the rear dail an image would zoom-in and show an exact area where the focus being acquired. If this area is not in focus it could be handshake, motion blur or AF failure.



#20 leospek

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Posted 14 March 2017 - 03:08 PM

I have exactly the same problem with my X-T1 and 16-55mm and 18-135 as well. And others have too :-(( Seek in forums..- for instance: https://www.dpreview.../thread/3864634

Shortly: on tripod, aperture 5.6-8, landscape shooting(distant objects), autofocus-"small zone". Priority is focusing - not release!! Each time you receive focus confirmation - green led.

From 20-25 shots you have about 30% blurred photos. Very sad. Not happens with prime lens - 16mm or 23mm. The only way to correct it is to do doubled shots.





Also tagged with one or more of these keywords: AF, Autofocus, X-T2, sharpness, focus, blurry