Sigma 35mm F1.4

[drb]

Hey Guy, that sounds really useful, thank you! But I am not sure I quite understand the process for getting around the bug. Does the bug only affect this lens? And what exactly is the sequence you used? Sorry to ask for it again but am being thick!

I'll second that, please clarify more about this bug and the workaround when you get a minute, thanks!

BTW, I focus calibrated my 35 f1.4 using the Focal software and it came out at with an AF tune of -4.

 

[Guy Mancuso]

Will do tonight basically turn AF fine tune off than turn camera off than turn AF back on and start from scratch at zero

 

[Guy Mancuso]

Alright if you want to recalibrate a lens you already done. Start by setting AF back to zero on that lens. Than turn AF fine tune off. Than turn camera off. Now turn camera on than AF fine tune back on than calibrate lens again. I did this and it jumped to -15 from -20 and looked pretty good. But I still want my number like -5 so had him look at it one more time.

 

[D&A]

Guy:

Sightly OT, but let us know what you think of the Sigma repair facility after you get your lens back. I'm assuming it's Cris Camera Services in Chandler. While I've only taken a few shots with my Sigma 35 f1.4 and it seems good, I do have the relatively new Sigma 150mm macro that seems to have auto focus issues and I was planning on sending it the same facility. It would be great to hear what you think of their work.

Hi drb,

Earlier in this thread I posted some comments regarding CRIS which I thought might be helpful and partly address your question.

Dave (D&A)

 

[D&A]

Alright if you want to recalibrate a lens you already done. Start by setting AF back to zero on that lens. Than turn AF fine tune off. Than turn camera off. Now turn camera on than AF fine tune back on than calibrate lens again. I did this and it jumped to -15 from -20 and looked pretty good. But I still want my number like -5 so had him look at it one more time.

Extremely useful Guy thanks...but ultimately the question is whether the softness seen on the right side with your lens has been address (corrected) even though Af fine tune has been reset to -15 from it's original -20.

Should I wait up till 4am in the morning for your announcing the results or have all the CRIS techs gone home for the night and they'll look at your lens again in the morning...LOL!

Dave (D&A)

 

[Guy Mancuso]

I sent them home to see there kids but they got till 9 am to fix it. I'm a nice guy but not that nice. Lol

 

[Guy Mancuso]

Seriously I'm going to fully test it out and redo a wall to check this skew issue I had. My bet is that was the mechanical adjustment. They did say they where worried they would have to send to Sigma but I think they got the firmware from Japan. I want the techs ear and see what he has done

 

[drb]

Hi drb,

Earlier in this thread I posted some comments regarding CRIS which I thought might be helpful and partly address your question.

Dave (D&A)

Thanks Dave, I saw your posts afterwards. I'm guessing that it's easier to get top service from Cris Camera if you are in a position to walk in there and "break some glass" if things aren't done quite right :deadhorse:

 

[D&A]

Seriously I'm going to fully test it out and redo a wall to check this skew issue I had. My bet is that was the mechanical adjustment. They did say they where worried they would have to send to Sigma but I think they got the firmware from Japan. I want the techs ear and see what he has done

Guy,

I can see where an update in firmware can help in recalibrating a lens whereby it no longer extends beyond the -20 (or + 20 for that matter) with regards to the AF fine tune adjustment in a particular body. Yet when there is asymmetry and optical misalignment causing causing softness on one side of a image, I can't imagine anything helping except an actual physical adjusment of the lens.

Dave (D&A)

 

[Guy Mancuso]

My thoughts as well.

 

[tashley]

Guy,

I can see where an update in firmware can help in recalibrating a lens whereby it no longer extends beyond the -20 (or + 20 for that matter) with regards to the AF fine tune adjustment in a particular body. Yet when there is asymmetry and optical misalignment causing causing softness on one side of a image, I can't imagine anything helping except an actual physical adjusment of the lens.

Dave (D&A)

That would seem intuitively correct but I wonder of sometimes it might work. These asymmetries can come and go according to really very slight changes of focus, or rather, be masked as the inclusion or exclusion of subject areas into areas of marginal DOF changes. We don't expect sharp edges on a lens like this until f4 for sharp-ish, f5.6 for sharp and f8 for really sharp, and so slight asymmetries can sometimes be largely veiled at wider apertures by general peripheral de-focus and largely hidden in DOF at f8 and possibly f5.6 so in my experience it is f4 and 5.6 that is the danger zone and even there, if the asymmetry is slight, there's a chance that an AFFT can deal with it.

Do a Reikan test on some lenses and the top of the curve can be quite flat. F&R zooms, for example, you might find that the short end needs a plus 12 and the short end a plus 6, but that both of those values are at the apex of a flat-ish part of the curve, in which case a plus 9 might work for both ends. So it is with mild asymmetries. The joker here, of course, is that you can't easily use Reikan with this bug. However, there is some stuff on the Internet to the effect that specifically this bug affects only the second and subsequent sigma lenses you enter an AFFT for: so if you Delete Saved Value and then start again, you can make the camera forget that there was ever a previous sigma lens and think only about your current one.

I am sure that most techs, when faced with a mild asymmetry, will try and tune it out with firmware and see if that makes the customer happy...

EDIT: adding sample images after using Guy's technique for getting round the FW bug.

Here are two shots that show pretty clearly what I mean. They are handheld at F4 and f5.6 and then a focus mask is added in Capture One. This camera is now accurately adjusted to +20 for my new copy of the Sigma, which was previously showing a very slight weakness on the left.

Observations: firstly, ignore the tower, it isn't in great focus on either shot (better in F5.6). Focus was on the nameplate of the little monument, centre. The grass 'mask' is pretty accurate but at the very granular level, the lens focusses very slightly closer on the left. I have confirmed this somewhat with other tests but need to do some with extreme rigour. Nonetheless I am fairly confident.

Note that the field of focus is croissant-shaped, as is very often the case. What this means is that there IS a line, parallel to the sensor, in a perfectly adjusted lens, at F4 and tighter, where everything is in pretty good focus in the same plane as the subject. But if your AF FIne Tune is off and the croissant is placed too far forward in the field, then the edges of that line will fall into the defocus area. getting AFFT just right has shifted the croissant backwards so that all of that parallel line is 'in the zone' but this is very very finely judged. For example, this lens now passes a brick wall test, just, because I have placed the croissant as far back as I safely can (the lens still focusses pretty well on centre wide open). However if I switch to Live View AF, the camera moves the croissant forwards and the edges of the wall, even at F5.6, are a little out of focus and slightly more so on the left because the slight decentering means that the croissant is twisted very slightly closer to the camera on the left.

My conclusion, subject to further testing at other distances, is that this lens does need attention but more because the AFFT value required is +20. However, an adjustment to the slight decentering would mean that I could notch the fine tune forward a touch and get slightly more reliable results in overall use. For me this shows that careful AFFT can under certain circumstances 'hide' slight lens asymmetry and possibly even negate the need for a repair. Given that almost no lenses have perfect alignment of all elements and groups, it's a judgement call as to when the effect can be worked around and when it needs fixing. SO I will be interested to see what happens with Guy's.

All this goes to show that to get the very best results from these systems requires quite an anal retentive approach, a lot of thought and quite some work! Luckily, few subject 'shapes' will show an effect like this noticeably. Regarding the fact that Live View tends to place the croissant too far forward, I will experiment with using magnified focus on a point half way to the edge: that should get a good compromise.

 

[Jan Brittenson]

I always AF tune for the AF point to be in best focus, then compensate for field curvature and DoF when I shoot. But it's a matter of taste of course.

I'm hard pressed to tell your lens focuses closer on the left side, especially given that you shot hand held and the ground isn't a perfect plane. It's neither level or flat on a hill like that. So I'd just stop down, shoot, check, adjust, reshoot and at some point further improvements are pointless.

 

[D&A]

Tim Wrote--->>>"For me this shows that careful AFFT can under certain circumstances 'hide' slight lens asymmetry and possibly even negate the need for a repair."<<<

That was basically the point I was trying to make. Sure certain aspects of asymmetry might be masked by adjusting/changing the AFFT through firmware and if it works, then all well and good. I too have experienced the changes you described by adjusting AFFT to somewhat ameliorate the affects of a slightly decentered lens. Of course the asymmetry is still there, just not as evident by the changing shift in the depth of field at a given f-stop.

It's of course very subject dependent in terms of what fills the frame, especially towards the sides & edges and a whole host of other image related characteristics.

Dave (D&A)

 

[Guy Mancuso]

Okay the folks at C.R.I.S. are really nice . There head technician called me today and basically he has this thing just about perfect but still he was not happy. He ran it outside on a D700 and at distance at 1.4 was not getting good results which i noticed as well. The firmware that Sigma is speaking of is a left/right AF point issue with the D800/D800E he does not have that firmware and with talks in Japan they are working on it but that is not my issue with the lens. Now at 2.8 and smaller apertures the lens is awesome both close and at distance but he wants to hold it another day and talk to Sigma again and discuss what they feel could be the issue. He is also not surprised as i mentioned a big gap between the 1st batch out and the long delay in the second batch that is due out. Sounds like Tim may have got a second batch version on the replacement. Now most of us shoot at distance stopped down and he wanted me to know that at the wider apertures he was uncomfortable about giving it back right now. They worked on one other 35mm but in Canon mount and sort of the same issue that one went back toSigma. The problem he said is they are so new that all the repair shops have not been exposed to working on them as well but he ran a slope test and a resolution test and he did say this thing is very very good. Once again i seem to be in the guinea pig position but Im okay with that. The is not the repair shops fault and if anything they are being extremely good about getting this dead on for me. We talked for about 15 minutes so it was really nice to get to chat over this. Keep you posted more

 

[Guy Mancuso]

BTW nice review and NO focus shift. Im glad I bought it

Sigma AF 35mm f/1.4 DG HSM (Nikon FX) - Review / Test Report

 

[D&A]

Guy,

Nice to hear this about C.R.I.S. I suspect a lot of this excellent service and interaction has to do with your personally being able to interact with them.

I'm curious and would like to know more (as I'm sure others would too), about what this particular Sigma firmware for the lens with specific regards to the D800/e left side focus sensor issue, is all about?

As well known, the left side focus point issue with D800/e bodies is random and not all bodies are effected and when they are, they vary greatly from body to body. Since a lens when sent in for adjustment or repair is generally done without a body, what does this 35mm f1.4 Sigma specific firmware accomplish when adjusting a 35mm f1.4 (the one that has to do with the D800/e left side sensor issue)? All I can think of is if someone sends in their D800/e along with a Sigma 35mm f 1.4 that needs adjusting, the firmware interacts with both the specific D800/e /lens combo and compensates for any left side sensor issue that particular body has.

If no body is sent in and it's simply adjustment of the lens...not sure how being interactive with the D800/e sensor plays a role in adjustment of the lens alone. This is only a guess on my part. Maybe firmware that also allows compensation of a lens for a D800/e's left side sensor that's "off" is simply a optional feature of Sigma's latest firmware for the 35mm f1.4 lens? Sounds interesting though.

Guy, I almost typed that we expect a 75 page detailed written report (double spaced of course) from you by morning...but then though that request might be grounds for being banned....LOL!

Dave (D&A)

 

[tashley]

Guy,
Guy, I almost typed that we expect a 75 page detailed written report (double spaced of course) from you by morning...but then though that request might be grounds for being banned....LOL!

Dave (D&A)

Are you trying to get us all killed ?

:ROTFL::ROTFL::ROTFL:

 

[tashley]

I'm hard pressed to tell your lens focuses closer on the left side, especially given that you shot hand held and the ground isn't a perfect plane. It's neither level or flat on a hill like that. So I'd just stop down, shoot, check, adjust, reshoot and at some point further improvements are pointless.

"at the very granular level, the lens focusses very slightly closer on the left. I have confirmed this somewhat with other tests but need to do some with extreme rigour. Nonetheless I am fairly confident."

Actually as a down and dirty indication, this is quite a good scene: the rising ground makes the 'croissant' easy to demonstrate in a rough way. Of course it's not lab-accurate! But then, all the lab-based reviews I have read of this lens say that it has very low field curvature whereas this test indicates, and other tests confirm, that in the field it can be significant.

 

[Guy Mancuso]

At repair shop brought my D800e and lens is off quite a bit . Testing both now and should be adjusting it. Running slope tests and resolution tests. These folks are really nice . Could not be more honest and helpful.

 

[Guy Mancuso]

Geez the tech came out with camera and lens along with a sledge hammer. Big smile on his face and Pronounced it all fixed just needed a big adjustment. ROTFLMAO