Sigma 50mm Art 1.4 Focusing problems

[kaihp]

Cameras are awesome devices, but they don't work by magic. Knowing a little bit about how the body and lens interact can be helpful in understanding and evaluating potential problems. The body detects how much out-of-focus an image is and sends a signal to the lens to adjust it, in one go in case of phase AF.

This (open loop focusing) was true previously, but Roger Cicala have found that newer Canon cameras do closed loop focusing (ie the PDAF system confirms the focus after the lens has moved).

 

[epsiloneri]

This (open loop focusing) was true previously, but Roger Cicala have found that newer Canon cameras do closed loop focusing (ie the PDAF system confirms the focus after the lens has moved).

Yes, that's right.

 

[candyman]

I have read lots and lots of threads here with people having AF problems with the 50A, but so far all of them had these issues with their 1D series camera, most notably the 1Dx.

Can someone confirm that these issues also affect other cameras as well?

IsaacImage also mentioned having difficulties on the 5DIII, which has a similar AF system. Being able to nail thin DOF shots with outer focus points is such a advantage that I don't think I'm willing to go back to using centerpoint only (i.e. 5DII) even if the lens is superior.

Let's not forget that there are also people using a 5D MK III and do not have any problem with the 50Art. Mine works great. Couldn't be happier.
Just for the record, works great on my 6D too.

 

[Viggo]

Assuming that you can use the Sigma Dock to get the lens perfect on a 5D MK III, it may still be horrible on a 7D or 1D MK IV. That's the limitation of the dock, it adjusts for one camera only.

Actually no, it adjusts the lens not the lens to a body. So the only thing you adjust is the normal afma. If my 1dx is at 0 and the lens adjusted at each distance to match that in camera adjustment, only thing I adjust on the 5d2 is the difference between those two bodies like I would any other lens. My gf's 5d2 is around -5 off the 1dx values. Dock adjusted lens and -5 in camera and it works.

It adjusts the lens to match the camera its on. That's what I was saying. It then can be close, or way off on a different camera. It depends on the actual adjustment accuracy of the camera you adjust it to.

I had a new 35mmL that was -2 on my 5D MK II but +17 on my 1D MK III. Canon adjusted it for me, and it was right-on for both, and also at 0 AFMA when I upgraded to a 5D MK III. I never could understand that.

At plus five for the 5D MK III, that's fine. But, if the lens changes over time, as some suggest, you have to recalibrate everything.

Yeah, but it's the same with a 35 L like you mention or the 50 Art or any other lens. The different afma values is about the lens , not the camera. And let's say my 50 misses with +20 at infinity, but that value works. And all the other values work, that's set in the lens. Now move it to a camera needing another +20 in general, that can be done. +20 in camera and +20 in lens. There's no difference in calibrating the 50 Art to a camera once the internal afma values are corresponding to each other. A camera doesn't really now what I set the 4 values to in my dock, and so it it's equal all over, only thing left to do is your normal afma. And as with any other lens, if it needs more than -+20, send it in.

And it seems clear that the drifting afma is with defective Sigma's, bit the working ones.

 

[Random Orbits]

I have read lots and lots of threads here with people having AF problems with the 50A, but so far all of them had these issues with their 1D series camera, most notably the 1Dx.

Can someone confirm that these issues also affect other cameras as well?

IsaacImage also mentioned having difficulties on the 5DIII, which has a similar AF system. Being able to nail thin DOF shots with outer focus points is such a advantage that I don't think I'm willing to go back to using centerpoint only (i.e. 5DII) even if the lens is superior.

Let's not forget that there are also people using a 5D MK III and do not have any problem with the 50Art. Mine works great. Couldn't be happier.
Just for the record, works great on my 6D too.

Yes, so it could be firmware dependent, or depend on some other settings in the camera. Face it, it is more likely that all the lenses are the same, and that they are not having a QC issue and that there is something hokey in their reverse engineered software that does NOT work for every combination.

 

[YuengLinger]

As far as firmware in the cameras go, remember a recent update to the 5DIII that resulted in aftermarket batteries not registering properly? Not showing charge remaining?

In fact, the charger that comes with the latest 5DIII's apparently had a similar "fix," where they won't even charge aftermarket batteries that were made prior to the firmware update. You just get a rapidly blinking light no matter how often you fool with removing, unplugging, etc. Same batteries in older chargers work fine.

So, ok, despite my skepticism, I do see the likelihood of a big corporation like Canon protectively taking steps to make AF hard as heck for independent lens makers.

And, IssacImage, by the way, I should have mentioned how great your photography is, despite my "suggestions" regarding your blogging. Beautiful images, consistently.

 

[Sella174]

The lens must give a camera a Canon lens code, and then the camera applies corrections and limitations based on a data table in the camera, so different camera generations might have some issues.

Is this true? Then that would explain the difficulties I had with the 40mm STM on my old cameras ...

 

[IsaacImage]

The lens must give a camera a Canon lens code, and then the camera applies corrections and limitations based on a data table in the camera, so different camera generations might have some issues.

Is this true? Then that would explain the difficulties I had with the 40mm STM on my old cameras ...

Appreciate this

 

[Viggo]

Yeah, but it's the same with a 35 L like you mention or the 50 Art or any other lens. The different afma values is about the lens , not the camera. And let's say my 50 misses with +20 at infinity, but that value works. And all the other values work, that's set in the lens. Now move it to a camera needing another +20 in general, that can be done. +20 in camera and +20 in lens. There's no difference in calibrating the 50 Art to a camera once the internal afma values are corresponding to each other. A camera doesn't really now what I set the 4 values to in my dock, and so it it's equal all over, only thing left to do is your normal afma. And as with any other lens, if it needs more than -+20, send it in.

The AFMA value is a product of the camera and lens.

Tiny changes in how the camera is manufactured (the sensor being half a mm closer or further away from the lens mount, for example) can also impact the AFMA value. It isn't just the lens and the variability in where the glass is within the lens relative to the mount on the back.

If it were only the lens then every camera would have the same AFMA value for any given lens and it doesn't work like that.

Not what I meant either. The four different distance afma settings you set in the new sigma lenses with the docking are there no matter what camera you mount it to. So if it's front focusing at 0,7 meters, dead on at 0,4m and for example back focus on infinity, that relationship will be the same no matter what the needed afma is. And that means when it's adjusted to hit at all those four distances, you can offset the entire range by using in camera afma, but not affect those four afma settings in camera at all. So it's not very important to which body you adjust those settings to, as long as it hits focus at every distance with that body. Changr body and do a normal afma in camera and still works withouy you ever knowing what the afma values at those four distances was set to.

 

[longdrive70]

I am happy to report my "first batch" copy is performing perfect! 5,000 captures an no variation noticed on the autofocus. ;D

 

[Shane1.4]

Zero issues with it on my 5dmkiii or 6d.

 

[Viggo]

Mine is still going strong also.

 

[Viggo]

Mine seems to have a very consistent front focusing issue with the two outermost points on each side of the frame. It appeared sharp when out in the sun, kind of hard to properly see the screen, but when I saw them on my computer a whole day of front focused pictures. I like to use the two outer points to frame vertically with my kids, but I say 95% is slightly front focused .

If I use center point it's extremely accurate and sharp. So Sigma, how do you adjust for that?

*edit* looks like going back to my old setup with the 4 point expansion helps a great deal with the outer points, along with Case 2 for static objects. This lens is VERY sharp wide open in the corners.

It's a real shame with the poor quality control that has always plagued Sigma is still there. But get a great copy and you have an EPIC lens.

 

[YuengLinger]

Viggo, those of us still waiting appreciate your updates, and this latest, how you try different AF settings for better results, is another helpful one.

I think the strongest selling point of this lens for me is its sharpness across the frame, so being able to compose with at least any of the 5DIII's cross-points is an essential part of how I imagine using it. Hopefully this won't be just a dream as AF issues get addressed...

 

[Viggo]

Viggo, those of us still waiting appreciate your updates, and this latest, how you try different AF settings for better results, is another helpful one.

I think the strongest selling point of this lens for me is its sharpness across the frame, so being able to compose with at least any of the 5DIII's cross-points is an essential part of how I imagine using it. Hopefully this won't be just a dream as AF issues get addressed...

You can't really trust the two outer points on each side, the one next to center is okay, but only center is fully trusted. And that kind of defeats the purpose of corner sharpness... The 85 L keeps delivering at any AF point...

 

[wickidwombat]

Viggo, those of us still waiting appreciate your updates, and this latest, how you try different AF settings for better results, is another helpful one.

I think the strongest selling point of this lens for me is its sharpness across the frame, so being able to compose with at least any of the 5DIII's cross-points is an essential part of how I imagine using it. Hopefully this won't be just a dream as AF issues get addressed...

You can't really trust the two outer points on each side, the one next to center is okay, but only center is fully trusted. And that kind of defeats the purpose of corner sharpness... The 85 L keeps delivering at any AF point...

I've found the 5 center column double cross types all perform equally well, with the very outer points also seem off sometimes but if i only use cross type points performance is good still

 

[GMCPhotographics]

Viggo, those of us still waiting appreciate your updates, and this latest, how you try different AF settings for better results, is another helpful one.

I think the strongest selling point of this lens for me is its sharpness across the frame, so being able to compose with at least any of the 5DIII's cross-points is an essential part of how I imagine using it. Hopefully this won't be just a dream as AF issues get addressed...

You can't really trust the two outer points on each side, the one next to center is okay, but only center is fully trusted. And that kind of defeats the purpose of corner sharpness... The 85 L keeps delivering at any AF point...

I'm sorry to hear that Viggo, but with a Sigma lens it really doesn't suprise me. Been there, done that and bought and sold many of these Tee shirts.....as i've said before, the 120-300 f2.8 OS was the last straw for me. Hey, I've even sold my 12-24mm recently too. I'm now Sigma free.

 

[Viggo]

Viggo, those of us still waiting appreciate your updates, and this latest, how you try different AF settings for better results, is another helpful one.

I think the strongest selling point of this lens for me is its sharpness across the frame, so being able to compose with at least any of the 5DIII's cross-points is an essential part of how I imagine using it. Hopefully this won't be just a dream as AF issues get addressed...

You can't really trust the two outer points on each side, the one next to center is okay, but only center is fully trusted. And that kind of defeats the purpose of corner sharpness... The 85 L keeps delivering at any AF point...

I've found the 5 center column double cross types all perform equally well, with the very outer points also seem off sometimes but if i only use cross type points performance is good still

I very rarely use upper an lower in the center, but as they are the same I guess you're right about that.

If I have the time to try spot, single point, and
4 point expansion and 6-7 shots to get the shot
I will get it. But using an outer point for a portrait mode shot and I have only one chance, it's usually off.

 

[wickidwombat]

Viggo, those of us still waiting appreciate your updates, and this latest, how you try different AF settings for better results, is another helpful one.

I think the strongest selling point of this lens for me is its sharpness across the frame, so being able to compose with at least any of the 5DIII's cross-points is an essential part of how I imagine using it. Hopefully this won't be just a dream as AF issues get addressed...

You can't really trust the two outer points on each side, the one next to center is okay, but only center is fully trusted. And that kind of defeats the purpose of corner sharpness... The 85 L keeps delivering at any AF point...

I've found the 5 center column double cross types all perform equally well, with the very outer points also seem off sometimes but if i only use cross type points performance is good still

I very rarely use upper an lower in the center, but as they are the same I guess you're right about that.

If I have the time to try spot, single point, and
4 point expansion and 6-7 shots to get the shot
I will get it. But using an outer point for a portrait mode shot and I have only one chance, it's usually off.

are you talking about the outer most points or the outer most cross type is you make only cross type selectable?
have you tried with only cross types selectable?

 

[Viggo]

Viggo, those of us still waiting appreciate your updates, and this latest, how you try different AF settings for better results, is another helpful one.

I think the strongest selling point of this lens for me is its sharpness across the frame, so being able to compose with at least any of the 5DIII's cross-points is an essential part of how I imagine using it. Hopefully this won't be just a dream as AF issues get addressed...

You can't really trust the two outer points on each side, the one next to center is okay, but only center is fully trusted. And that kind of defeats the purpose of corner sharpness... The 85 L keeps delivering at any AF point...

I've found the 5 center column double cross types all perform equally well, with the very outer points also seem off sometimes but if i only use cross type points performance is good still

I very rarely use upper an lower in the center, but as they are the same I guess you're right about that.

If I have the time to try spot, single point, and
4 point expansion and 6-7 shots to get the shot
I will get it. But using an outer point for a portrait mode shot and I have only one chance, it's usually off.

are you talking about the outer most points or the outer most cross type is you make only cross type selectable?
have you tried with only cross types selectable?

First thing I selected when I bought the 5d3 and the first thing I did when I got the 1dx, I always only use crosstype .