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FORUMS Canon Cameras, Lenses & Accessories Canon EF and EF-S Lenses 
Thread started 16 Mar 2017 (Thursday) 06:53
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85 Art : AF issues false or not ? Many ?

 
Ilovetheleafs
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Apr 10, 2017 03:04 as a reply to  @ post 18317662 |  #16

It's massively over stated the Sigma focusing issues. I own 3 Sigma lenses and none have focusing issues.


Canon Rebel XS gripped, Canon 18 - 55mm, Sigma 18 - 200mm f3.5 - f6.3 DC OS HSM,Sigma 50mm f1.4 Olympus TG-810 Tough, LowePro Classified 160AW, Canon 430EX II Flash, Kata E-702

  
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Bobby ­ Juice
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Apr 10, 2017 22:48 |  #17

Ilovetheleafs wrote in post #18323998 (external link)
It's massively over stated the Sigma focusing issues. I own 3 Sigma lenses and none have focusing issues.

I just purchased the Sigma 85 1.4 ART earlier today and believe the same. I own a Sigma 18-35 1.8 ART. It's been my favorite lens and no focusing issues. I've owned a Sigma 24-70 in the past, no issues. Large expectations for this and hope they are met. So far from what I've read, it should.


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Ilovetheleafs
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Apr 11, 2017 14:22 as a reply to  @ Bobby Juice's post |  #18

Even my 7 almost 8 year old 18 - 200 has no focusing problems and that's one of the cheapest lenses they've made :P in fact it was the lens that got me into Sigma in the first place :P


Canon Rebel XS gripped, Canon 18 - 55mm, Sigma 18 - 200mm f3.5 - f6.3 DC OS HSM,Sigma 50mm f1.4 Olympus TG-810 Tough, LowePro Classified 160AW, Canon 430EX II Flash, Kata E-702

  
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View_Finder
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Post edited over 1 year ago by View_Finder.
     
Apr 12, 2017 20:27 |  #19

Ilovetheleafs wrote in post #18323998 (external link)
It's massively over stated the Sigma focusing issues. I own 3 Sigma lenses and none have focusing issues.

With all due respect, perhaps 3 lenses is not a large enough of a sampling to say that it is "massively over stated"? I'm open to the thought that there might be SOMETHING to the rumors of past AF issues. Yes, I think it might be overstated and exaggerated to some degree but there has to be a reason why the rumors started in the first place, right?

I had a Sigma 50mm f/1.4 EX DG HSM that had a slight AF issue. I knew how to compensate for it and it was no big deal for me. But it was something I had never experienced with any Canon lens. After many years, I finally sold it last year. I now have two Sigma lenses - one being the 85A. So far everything is great with both. Only time and hands-on testing will reveal to me, at least with these two lenses, whether or not these lenses work well for me. That is all I will be able to say.


5D4, 7D2, 16-35 f/4L IS, 24-70 f/2.8L II, 70-200 f/2.8L IS II, 100-400L IS II, 100 f/2.8L IS, 300 f/4L IS, 500 f/4L IS, 2xIII, Σ35A, Σ85A, Samyang 14 f/2.8 & 85 f/1.4
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panicatnabisco
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Apr 12, 2017 21:06 |  #20

They don't sell those docks for nothing lol


Canon 1DX | 6D | 16-35/2.8II | 24/1.4II | 24-70/2.8II | 24-105 | 50/1.8 | 50/1.2 | 70-200/2.8 IS II | 85/1.2II | 100/2.8 IS macro | 400/2.8 IS | 2xIII
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smythie
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Apr 12, 2017 21:45 |  #21

Yeah, their price is usually in the order of $50


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FEChariot
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Apr 12, 2017 23:19 |  #22

panicatnabisco wrote in post #18326525 (external link)
They don't sell those docks for nothing lol

These comments make no sense. You are trying to make a degrading funny yet it was Canon and Nikon putting the same kind of features in the camera body to have AFMA and fix focus issues long before Sigma or Tamron ever did. How else do you suggest third party manufacturers give you the features here? Maybe Canon will let them write code in their Camera OS?


Canon 7D/350D, Σ17-50/2.8 OS, 18-55IS, 24-105/4 L IS, Σ30/1.4 EX, 50/1.8, C50/1.4, 55-250IS, 60/2.8, 70-200/4 L IS, 85/1.8, 100/2.8 IS L, 135/2 L 580EX II, 430EX II * 2, 270EX II.

  
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Apr 13, 2017 01:52 |  #23

FEChariot wrote in post #18326593 (external link)
These comments make no sense. You are trying to make a degrading funny yet it was Canon and Nikon putting the same kind of features in the camera body to have AFMA and fix focus issues long before Sigma or Tamron ever did. How else do you suggest third party manufacturers give you the features here? Maybe Canon will let them write code in their Camera OS?

Canon lets Sigma lenses use the same AFMA feature in-body, therefore the dock is just a smart way to make users pay more for a lens that should have worked out of the box but did not.


1Dx, 5D2 and some lenses

  
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Ilovetheleafs
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Apr 13, 2017 02:22 as a reply to  @ CheshireCat's post |  #24

have you even LOOKED at the Dock? It's very different. It lets you MFA at multiple points of distance... not just one like Canon. Maybe do some research next time before giving advice.


Canon Rebel XS gripped, Canon 18 - 55mm, Sigma 18 - 200mm f3.5 - f6.3 DC OS HSM,Sigma 50mm f1.4 Olympus TG-810 Tough, LowePro Classified 160AW, Canon 430EX II Flash, Kata E-702

  
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05Xrunner
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Apr 13, 2017 08:14 |  #25

CheshireCat wrote in post #18326685 (external link)
Canon lets Sigma lenses use the same AFMA feature in-body, therefore the dock is just a smart way to make users pay more for a lens that should have worked out of the box but did not.

why dont you an ED go make a forum together with your crap post.
This is just 100% garbage. Sigma has to REVERSE engineer the electronics for the AF. Canon isnt giving them the code so it could make things harder to be perfect every time. The dock is a way that users can now adjust the lens almost perfect for their specific body at Multiple focal lengths and at multiple distance as well for extreme fine tuning. not just a global adjustment for the entire range of the lens on older bodies and new ones only have a global wide and tele adjustment. Stop trying to say a lens is defective cause it needs MA. Canon lenses need it as well and canon would be smart to come out with a dock of their own as well. If you have never had a lens needing ANY type of MA you are either in denial or dont even know that you need it


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Fuji X-T2, Fuji 18-55 2.8-4 OIS, Fuji 35 f2, Fuji 56 1.2, Fuji 90 f2, Fuji 55-200 3.5-4.8 OIS
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CheshireCat
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Post edited over 1 year ago by CheshireCat. (4 edits in all)
     
Apr 13, 2017 12:46 |  #26

05Xrunner wrote in post #18326842 (external link)
why dont you an ED go make a forum together with your crap post.
This is just 100% garbage. Sigma has to REVERSE engineer the electronics for the AF. Canon isnt giving them the code so it could make things harder to be perfect every time.

From Canon's documentation:

"What is AF Microadjustment?
It is a function that makes it possible to make fine adjustments for the focus system’s
plane of sharpest focus, for AF during viewfinder shooting.
[...]
AF Microadjustment occurs within each camera body, and not in the lens itself."


AFMA simply works by telling a lens to move in a different place than what the AF-sensor thinks is in focus. This breaks the closed-loop that makes a lens converge to the actual focus, so you can never be sure that this will work at any distance or focal length or focus point (let alone aperture, which may have problems also with no AFMA).

Like I have already explained multiple times, AFMA's original purpose was to compensate for AF-sensor vs image-sensor calibration issues.
In other words, AFMA was never meant to fix lenses, but just to fix bodies. So, it doesn't matter if the lens is Canon or Sigma: AFMA was created to fix bodies.

Then manufacturers found that AFMA could be useful to let the user handle issues with lenses themselves, and avoid lenses to be sent-in for calibration. So they introduced per-lens AFMA. This way, users like you are happy to "fix" (actually "compensate for") focus problems of different nature (focus-shift, decentered or tilted elements, miscalibrated AF motors) and will not send the lens in to be actually fixed.
I don't know what they do in the lens to implement this, but I guess they make the lens under/over-shoot the point that the AF-system asks the lens to move to. Again, I don't see how this cannot break the closed-loop, and therefore give consistent results.

So I respect your opinion, and I am happy if you love to shell out the extra money to buy a dock and "fix" the lens yourself.
However, you should respect my opinion too. And my opinion is that users like you are allowing third-party lens manufacturers to use lower tolerances and pocket the extra money.

No more third-party lenses for me, until I am not told "you should buy a dock" anymore.


1Dx, 5D2 and some lenses

  
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Charlie
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Apr 13, 2017 13:05 |  #27

CheshireCat wrote in post #18327046 (external link)
From Canon's documentation:

"What is AF Microadjustment?
It is a function that makes it possible to make fine adjustments for the focus system’s
plane of sharpest focus, for AF during viewfinder shooting.
[...]
AF Microadjustment occurs within each camera body, and not in the lens itself."


AFMA simply works by telling a lens to move in a different place than what the AF-sensor thinks is in focus. This breaks the closed-loop that makes a lens converge to the actual focus, so you can never be sure that this will work at any distance or focal length or focus point (let alone aperture, which may have problems also with no AFMA).

Like I have already explained multiple times, AFMA's original purpose was to compensate for AF-sensor vs image-sensor calibration issues.
In other words, AFMA was never meant to fix lenses, but just to fix bodies. So, it doesn't matter if the lens is Canon or Sigma: AFMA was created to fix bodies.

Then manufacturers found that AFMA could be useful to let the user handle issues with lenses themselves, and avoid lenses to be sent-in for calibration. So they introduced per-lens AFMA. This way, users like you are happy to "fix" (actually "compensate for") focus problems of different nature (focus-shift, decentered or tilted elements, miscalibrated AF motors) and will not send the lens in to be actually fixed.
I don't know what they do in the lens to implement this, but I guess they make the lens under/over-shoot the point that the AF-system asks the lens to move to. Again, I don't see how this cannot break the closed-loop, and therefore give consistent results.

So I respect your opinion, and I am happy if you love to shell out the extra money to buy a dock and "fix" the lens yourself.
However, you should respect my opinion too. And my opinion is that users like you are allowing third-party lens manufacturers to use lower tolerances and pocket the extra money.

No more third-party lenses for me, until I am not told "you should buy a dock" anymore.

in camera MFA isnt a global setting though, it's per lens


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smythie
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Post edited over 1 year ago by smythie.
     
Apr 13, 2017 18:25 |  #28

CheshireCat wrote in post #18327046 (external link)
From Canon's documentation:

"What is AF Microadjustment?
It is a function that makes it possible to make fine adjustments for the focus system’s
plane of sharpest focus, for AF during viewfinder shooting.
[...]
AF Microadjustment occurs within each camera body, and not in the lens itself."


AFMA simply works by telling a lens to move in a different place than what the AF-sensor thinks is in focus. This breaks the closed-loop that makes a lens converge to the actual focus, so you can never be sure that this will work at any distance or focal length or focus point (let alone aperture, which may have problems also with no AFMA).

Like I have already explained multiple times, AFMA's original purpose was to compensate for AF-sensor vs image-sensor calibration issues.
In other words, AFMA was never meant to fix lenses, but just to fix bodies. So, it doesn't matter if the lens is Canon or Sigma: AFMA was created to fix bodies.

Then manufacturers found that AFMA could be useful to let the user handle issues with lenses themselves, and avoid lenses to be sent-in for calibration. So they introduced per-lens AFMA. This way, users like you are happy to "fix" (actually "compensate for") focus problems of different nature (focus-shift, decentered or tilted elements, miscalibrated AF motors) and will not send the lens in to be actually fixed.
I don't know what they do in the lens to implement this, but I guess they make the lens under/over-shoot the point that the AF-system asks the lens to move to. Again, I don't see how this cannot break the closed-loop, and therefore give consistent results.

So I respect your opinion, and I am happy if you love to shell out the extra money to buy a dock and "fix" the lens yourself.
However, you should respect my opinion too. And my opinion is that users like you are allowing third-party lens manufacturers to use lower tolerances and pocket the extra money.

No more third-party lenses for me, until I am not told "you should buy a dock" anymore.

AFMA does not break any closed loop system. It applies a constant (plus or minus) to the position the camera asks the lens to move to. Whatever closed loop operation would occur without AFMA being applied, continues to operate: e.g.
1) Camera guesstimates that the lens needs to move to x position
2) due to an AFMA value of +2 (depending on body it might be a body global setting or a per lens setting) it tells the lens that it should go to position x+2
3) the lens moves and reports I've finished
3a) in the case of some of the newer Canon lenses (e.g. 24-70 mk2) and also on the body in question (1DX, 5D3 and newer, maybe also 7D2) the lens will report that it has arrived at y position
3b) if y =/= x+2 the camera will tell the lens to move again
3c) return to 3a until y = x+2
4) the camera re-checks whether the image is now "suitably in-focus"
5) depending on settings the camera either tries again and returns to step 1 all over again or it gives up.

No closed loop is broken because of an AFMA offset.


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Ilovetheleafs
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Apr 13, 2017 20:04 as a reply to  @ 05Xrunner's post |  #29

Agree with you on all of this except for the last part. Only lens of mine that needs AFMA is my Canon 18 - 55.


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CheshireCat
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Post edited over 1 year ago by CheshireCat. (6 edits in all)
     
Apr 13, 2017 23:32 |  #30

smythie wrote in post #18327273 (external link)
AFMA does not break any closed loop system. It applies a constant (plus or minus) to the position the camera asks the lens to move to. Whatever closed loop operation would occur without AFMA being applied, continues to operate: e.g.
1) Camera guesstimates that the lens needs to move to x position
2) due to an AFMA value of +2 (depending on body it might be a body global setting or a per lens setting) it tells the lens that it should go to position x+2
3) the lens moves and reports I've finished
3a) in the case of some of the newer Canon lenses (e.g. 24-70 mk2) and also on the body in question (1DX, 5D3 and newer, maybe also 7D2) the lens will report that it has arrived at y position
3b) if y =/= x+2 the camera will tell the lens to move again
3c) return to 3a until y = x+2
4) the camera re-checks whether the image is now "suitably in-focus"
5) depending on settings the camera either tries again and returns to step 1 all over again or it gives up.

No closed loop is broken because of an AFMA offset.

I don't think this is how AFMA works.

Keep in mind that the original purpose of AFMA was to fix AF-sensor vs image-sensor calibration problems.
Therefore step 4 cannot check for "suitably in focus" because what is in focus for the AF-sensor is not for the image-sensor.

What I think is that the closed-loop drives the lens until the image is in focus for the AF-sensor, then the camera breaks the closed-loop, and then applies the AFMA offset.
At this point, the camera is blind because it cannot use the AF-sensor to fine-tune focus anymore (in fact, it just misfocused on purpose by the AFMA offset), and can only hope that the offset will get the subject in focus on the image-sensor.

Since a single offset won't work at any subject distance, focal length, aperture, et cetera, AFMA is not the right solution.


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85 Art : AF issues false or not ? Many ?
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