Sigma 16mm 1.4 - focus problems at 2.8 and 5.6 in AF-S

trenzterra said:

rjjr said:

trenzterra said:

Conclusion

- Setting Effect OFF doesn't solve the problem completely
- Sure-fire fix is to use AF-C instead of AF-S. Use BBF if you want AF-S-like behaviour

Click to expand...

That's what I've been doing all along, it works perfectly.

trenzterra said:

- Alternatively, set Focus Priority to Release and don't use the EVF in situations where you really need AF-S.

Click to expand...

As I noted previously, I tried it and it didn't really fix it with EVF or LCD.

Click to expand...

Just wondering, is your focus priority set to Release instead of balance emphasis? That might be the issue.

Click to expand...

CyeJoeBob said:

trenzterra said:

CyeJoeBob said:

Here is an example of the focus problem at f/5.6 which I could find on both copy of the lenses I tested, though the second one was better and it did happen less often.

In the frame center, the focus difference is barely visible. But the border sharpness of the EVF focused image is much better.

100% center crop: left - EVF focused, right - display focused

100% border crop: left - EVF focused, right - display focused

Click to expand...

Does this only happen when focusing at infinity? I can't reproduce this issue at f5.6. which camera model?

Click to expand...

Sony A6300. It doesn't only happen at infinity. But it does seem to be gone at very close distances.

Click to expand...

trenzterra said:

Yeah I managed to replicate it at mid focus distance. If you test long enough I replicated it at EVF as well.

I am planning to use your post to write in to Sony and Sigma. Just to check--when you set to release priority, do you get focus issues at F2.8 using live view? Seems like I am experiencing the issue with release priority at f2.8. conversely, at f5.6, the porblem is gone with release priority but not with af or balanced emphasis.

AF-c you do lose some benefits of focusing, because it always focuses stopped down. so in certain situations af-s can be more beneficial. Sgkoala mentions that using focus magnification will help in this situation. I also think DMF may be beenficial to correct minor focus errors.

Click to expand...

CyeJoeBob said:

Euell said:

This is all very interesting and perhaps a bit disturbing. However, with wide angle lenses generally focus isn't usually a major issue due to depth of field. while the Sigma 16 is a very fast lens and there are, of course, exceptions, for most applications focus is simply not going to be an issue. If, on the other hand, the Sony 50mm f1.8 exhibits similar focus issues, that IS a serious problem.

Click to expand...

The problem is that it is an issue for landscape, because it is also happening at f/5.6 or even other apertures in AF-S. It only slightly misses the focus, which causes soft edges.

I now use BBF with AF-C for landscape if battery life matters. I set AF/MF button to Eye AF and AEL button to AF On. So I don't have to refocus every image and I'm still flexible if I want to focus closer. Focus and recompose is possible as well.

Click to expand...

AHM said:

CyeJoeBob said:

Euell said:

This is all very interesting and perhaps a bit disturbing. However, with wide angle lenses generally focus isn't usually a major issue due to depth of field. while the Sigma 16 is a very fast lens and there are, of course, exceptions, for most applications focus is simply not going to be an issue. If, on the other hand, the Sony 50mm f1.8 exhibits similar focus issues, that IS a serious problem.

Click to expand...

The problem is that it is an issue for landscape, because it is also happening at f/5.6 or even other apertures in AF-S. It only slightly misses the focus, which causes soft edges.

I now use BBF with AF-C for landscape if battery life matters. I set AF/MF button to Eye AF and AEL button to AF On. So I don't have to refocus every image and I'm still flexible if I want to focus closer. Focus and recompose is possible as well.

Click to expand...

What is BBF?

Click to expand...

AHM said:

CyeJoeBob said:

Euell said:

This is all very interesting and perhaps a bit disturbing. However, with wide angle lenses generally focus isn't usually a major issue due to depth of field. while the Sigma 16 is a very fast lens and there are, of course, exceptions, for most applications focus is simply not going to be an issue. If, on the other hand, the Sony 50mm f1.8 exhibits similar focus issues, that IS a serious problem.

Click to expand...

The problem is that it is an issue for landscape, because it is also happening at f/5.6 or even other apertures in AF-S. It only slightly misses the focus, which causes soft edges.

I now use BBF with AF-C for landscape if battery life matters. I set AF/MF button to Eye AF and AEL button to AF On. So I don't have to refocus every image and I'm still flexible if I want to focus closer. Focus and recompose is possible as well.

Click to expand...

What is BBF?

Click to expand...

CyeJoeBob said:

CyeJoeBob said:

Yeah I managed to replicate it at mid focus distance. If you test long enough I replicated it at EVF as well.

I am planning to use your post to write in to Sony and Sigma. Just to check--when you set to release priority, do you get focus issues at F2.8 using live view? Seems like I am experiencing the issue with release priority at f2.8. conversely, at f5.6, the porblem is gone with release priority but not with af or balanced emphasis.

AF-c you do lose some benefits of focusing, because it always focuses stopped down. so in certain situations af-s can be more beneficial. Sgkoala mentions that using focus magnification will help in this situation. I also think DMF may be beenficial to correct minor focus errors.

Click to expand...

With release priority the problem seemed to be gone at f/5.6 with my Sigma 16mm. But I did not test it for f/2.8. I used AF priority in all of my tests.

I already wrote to Sigma Germany last monday, with reference to this discussion. No answer so far.

Click to expand...

trenzterra said:

CyeJoeBob said:

trenzterra said:

Yeah I managed to replicate it at mid focus distance. If you test long enough I replicated it at EVF as well.

I am planning to use your post to write in to Sony and Sigma. Just to check--when you set to release priority, do you get focus issues at F2.8 using live view? Seems like I am experiencing the issue with release priority at f2.8. conversely, at f5.6, the porblem is gone with release priority but not with af or balanced emphasis.

AF-c you do lose some benefits of focusing, because it always focuses stopped down. so in certain situations af-s can be more beneficial. Sgkoala mentions that using focus magnification will help in this situation. I also think DMF may be beenficial to correct minor focus errors.

Click to expand...

With release priority the problem seemed to be gone at f/5.6 with my Sigma 16mm. But I did not test it for f/2.8. I used AF priority in all of my tests.

I already wrote to Sigma Germany last monday, with reference to this discussion. No answer so far.

Click to expand...

Just wondering if you could retry some shots in live view at f/2.8 with Focus Priority set to release?

Sigma Singapore has gotten back to me and asked me to go down to their service centre to let their engineer test. Don't have time to go down at the moment but will try next week.

Click to expand...

CyeJoeBob said:

Euell said:

This is all very interesting and perhaps a bit disturbing. However, with wide angle lenses generally focus isn't usually a major issue due to depth of field. while the Sigma 16 is a very fast lens and there are, of course, exceptions, for most applications focus is simply not going to be an issue. If, on the other hand, the Sony 50mm f1.8 exhibits similar focus issues, that IS a serious problem.

Click to expand...

The problem is that it is an issue for landscape, because it is also happening at f/5.6 or even other apertures in AF-S. It only slightly misses the focus, which causes soft edges.

Click to expand...

Euell said:

CyeJoeBob said:

Euell said:

This is all very interesting and perhaps a bit disturbing. However, with wide angle lenses generally focus isn't usually a major issue due to depth of field. while the Sigma 16 is a very fast lens and there are, of course, exceptions, for most applications focus is simply not going to be an issue. If, on the other hand, the Sony 50mm f1.8 exhibits similar focus issues, that IS a serious problem.

Click to expand...

The problem is that it is an issue for landscape, because it is also happening at f/5.6 or even other apertures in AF-S. It only slightly misses the focus, which causes soft edges.

Click to expand...

That would be a flatness of field issue, rather than a focus issue.

Click to expand...

sgkoala said:

trenzterra said:

sgkoala said:

trenzterra said:

I went outside to a more open area to test again. Strange thing is that now I notice, even at f2.8, there is still focus inaccuracy with setting effect set to OFF. this happens only at further distances. At close distances the camera seems to work fone. With setting effect off. This means perhaps the issue is not resolved completely...

Click to expand...

Agree with your findings! Just retested with flexible spot medium on a stained glass window at quite a far distance away. F2.8, PAL.

1. AF-S, setting effect ON. Out of focus

2. AF-C, setting effect ON, Perfect focus

3. AF-S, setting effect OFF, Out of focus

Then, to check in case of any focus shift (since I believe setting effect OFF focuses wide open?)

4. Manual focus at F1.4, Perfect focus

5. Changed aperture to F2.8 and hit shutter without refocusing, still in perfect focus. Hence no focus shift.

Retested on the 30/1.4 at f2 on same stained glass window and also found that AF-S, setting effect OFF was Out of Focus.

I also realised that manual focussing with the 16/1.4 lens is not very sensitive? Really weird, it kind of jumps in steps so I can’t make very very fine adjustments. The 30/1.4 on latest firmware doesn’t have this issue.

Conclusion - AF-C still the safest at wide apertures...

Click to expand...

Yes, that seems to be the conclusion. I also realise that yes, live view also manifests the problem at far distances, not just EVF.

But it's kinda strange... Because I don't remember experiencing this a few weeks ago. Or maybe I just shot one shot and saw it was in focus and never tried again.

Click to expand...

OK I just did more tests on the same stained glass window:

F2.8, LCD:

1. AF-S vs 2. AF-C: the AF-C image looks perfect. The AF-S image looks in focus, but I see a slight softness that is visible over the whole image only when zooming 1:1 and doing direct comparison. Interestingly I see a slight contrast loss in the AF-S image vs the AF-C image even without zooming in, and I don't think the lighting changed in those few seconds (the exposure is the same and Brightness Value of 9.7 vs 9.66).

F5.6, LCD:

3. AF-S vs 4. AF-C: the AF-C image looks perfect. The AF-S image has a slight softness over the whole image when viewed at 1:2, which becomes obvious when zoomed at 1:1 (much softer than the F2.8 LCD shot, but much less out of focus than the F2.8 AF-S EVF shot ). Same slight contrast loss as I observed at F2.8.

Conclusion: AF-C still the safest

Unfortunately I can't post these images as they may reveal where I live a bit too close for comfort.

Click to expand...

sgkoala said:

Euell said:

CyeJoeBob said:

Euell said:

This is all very interesting and perhaps a bit disturbing. However, with wide angle lenses generally focus isn't usually a major issue due to depth of field. while the Sigma 16 is a very fast lens and there are, of course, exceptions, for most applications focus is simply not going to be an issue. If, on the other hand, the Sony 50mm f1.8 exhibits similar focus issues, that IS a serious problem.

Click to expand...

The problem is that it is an issue for landscape, because it is also happening at f/5.6 or even other apertures in AF-S. It only slightly misses the focus, which causes soft edges.

Click to expand...

That would be a flatness of field issue, rather than a focus issue.

Click to expand...

It doesn’t appear to be. I saw a softness over the entire image, at f5.6 when using AF-S and LCD to focus, focus distance near infinity. In my test image I could not see a single part of the image that was very sharp, while at the same time, it wasn’t so out of focus to be noticeable without zooming in. It’s a curious issue.

The issue is completely absent when using AF-C (and I think AF-S with EVF but need to retest to be sure) at the same aperture f5.6.

Click to expand...

Euell said:

sgkoala said:

Euell said:

CyeJoeBob said:

Euell said:

This is all very interesting and perhaps a bit disturbing. However, with wide angle lenses generally focus isn't usually a major issue due to depth of field. while the Sigma 16 is a very fast lens and there are, of course, exceptions, for most applications focus is simply not going to be an issue. If, on the other hand, the Sony 50mm f1.8 exhibits similar focus issues, that IS a serious problem.

Click to expand...

The problem is that it is an issue for landscape, because it is also happening at f/5.6 or even other apertures in AF-S. It only slightly misses the focus, which causes soft edges.

Click to expand...

That would be a flatness of field issue, rather than a focus issue.

Click to expand...

It doesn’t appear to be. I saw a softness over the entire image, at f5.6 when using AF-S and LCD to focus, focus distance near infinity. In my test image I could not see a single part of the image that was very sharp, while at the same time, it wasn’t so out of focus to be noticeable without zooming in. It’s a curious issue.

The issue is completely absent when using AF-C (and I think AF-S with EVF but need to retest to be sure) at the same aperture f5.6.

Click to expand...

I was responding to CyjoeBob's observation above, who described only soft edges.

Click to expand...

Mike_Italy said:

Received my sigma 16mm f1.4 and just start testing the claimed issue.

Tried afs with live view effect off: olthough it improves the focus compared the worst results (evf+afs) the accuracy is not 100%, slight oof is still visible

Tried afs with focus magnifier (live view effect on) and all pictures are tack sharp

Preliminary conclusion is that if you really need afs and evf the focus magnifier is what you need to avoid oof pictures

Hope this help

Click to expand...

snapa said:

Mike_Italy said:

Received my sigma 16mm f1.4 and just start testing the claimed issue.

Tried afs with live view effect off: olthough it improves the focus compared the worst results (evf+afs) the accuracy is not 100%, slight oof is still visible

Tried afs with focus magnifier (live view effect on) and all pictures are tack sharp

Preliminary conclusion is that if you really need afs and evf the focus magnifier is what you need to avoid oof pictures

Hope this help

Click to expand...

Yes, it helps a lot! I need a fast/sharp 16mm lens for indoor/low light shooting, and was hoping someone would test it using Focus Magnifier (FM). I use DMF with FM 90% of the time with my Sony 70-300G lens for wildlife. I suppose I could do the same with the Sigma 16mm when shooting still subjects. If shooting indoors with moving people, I suppose I could be forced to use the 'Work Around' AF-C in those situations :-|

If anyone else could do the same test using AF-S with FM, it would be greatly appreciated. Thanks again for your time and testing of the lens, much appreciated!

Click to expand...

sgkoala said:

snapa said:

Mike_Italy said:

Received my sigma 16mm f1.4 and just start testing the claimed issue.

Tried afs with live view effect off: olthough it improves the focus compared the worst results (evf+afs) the accuracy is not 100%, slight oof is still visible

Tried afs with focus magnifier (live view effect on) and all pictures are tack sharp

Preliminary conclusion is that if you really need afs and evf the focus magnifier is what you need to avoid oof pictures

Hope this help

Click to expand...

Yes, it helps a lot! I need a fast/sharp 16mm lens for indoor/low light shooting, and was hoping someone would test it using Focus Magnifier (FM). I use DMF with FM 90% of the time with my Sony 70-300G lens for wildlife. I suppose I could do the same with the Sigma 16mm when shooting still subjects. If shooting indoors with moving people, I suppose I could be forced to use the 'Work Around' AF-C in those situations :-|

If anyone else could do the same test using AF-S with FM, it would be greatly appreciated. Thanks again for your time and testing of the lens, much appreciated!

Click to expand...

Click to expand...

sgkoala said:

snapa said:

Yes, it helps a lot! I need a fast/sharp 16mm lens for indoor/low light shooting, and was hoping someone would test it using Focus Magnifier (FM). I use DMF with FM 90% of the time with my Sony 70-300G lens for wildlife. I suppose I could do the same with the Sigma 16mm when shooting still subjects. If shooting indoors with moving people, I suppose I could be forced to use the 'Work Around' AF-C in those situations :-|

If anyone else could do the same test using AF-S with FM, it would be greatly appreciated. Thanks again for your time and testing of the lens, much appreciated!

Click to expand...

AF-S with Focus Magnifier (where you place the cross-hair on the subject while in magnified view, then trigger AF) is 100% accurate on both the Sigma 30/1.4 and 16/1.4, at all apertures and focus distances I tested. Caveat - need enough contrast in order for it to focus at all, although same is true for all lenses in this mode.

My approach with this lens (and Sigma 30/1.4) is follows:

- AF-C by default (works 90% of time)

- If AF-C is hunting due to aperture too small etc, switch to AF-S. Usually I would already be outside the problem apertures so this is sufficient.

- If using EyeAF in AF-C and it hunts, I will switch to AF-S and use EyeAF at any aperture, as I have tested EyeAF is reliably accurate.

The above two settings cover 9% of the remaining 10%, so the below workarounds are quite rarely needed.

- If I am not using EyeAF and AF-C still hunts and it’s a problem aperture (eg for me, F1.6-F2 on 30/1.4 or F2.5-F2.8 on 16/1.4) OR if I want to use the LCD to focus rather than EVF, I switch to AF-S and use AF in Focus Mag.

- If in the above it cannot focus in AF in Focus Mag due to too low light / low contrast, OR Focus Mag is not practical as there is some subject movement, I will either use AF-S with LCD to focus (if focus distance is close, pretty confident this is accurate), or as last resort (eg further away focus distance where LCD may be inaccurate) use a different aperture eg F2.2 instead of F2.5, or F3.2 instead of F2.8.

Click to expand...

Mike_Italy said:

Received my sigma 16mm f1.4 and just start testing the claimed issue.

Test conditions:

Tripod

Distance from the focused obj 60cm

F2.8

In these conditions the oof is very consistent using afs and evf

Using afs and monitor to focus the oof disappear completely

Tried many settings to find out the best for afs usage

Tried afs with live view effect off: olthough it improves the focus compared the worst results (evf+afs) the accuracy is not 100%, slight oof is still visible

Tried afs with focus magnifier (live view effect on) and all pictures are tack sharp

Preliminary conclusion is that if you really need afs and evf the focus magnifier is what you need to avoid oof pictures

Hope this help

Click to expand...