# Sigma flaw... Accept it, learn how to fix it, or upgrade?



## andrewdoeshair (Jun 20, 2017)

Sorry to bug you with a problem I could eventually figure out through google and youtube. I'm just hoping one of you has been through this and can save me a few hours of Internetting...

I've got a Sigma 50mm Art lens that I use on my 5Diii and most of the time I love it, but I spend a good chunk of time hating it. I recently took a trip to Ireland and brought my Canon 50mm F1.8 instead of the Sigma just because I didn't want to lug around so much weight, and I was very happy with the performance. Sometimes the bokeh was a bit jarring and the contrast was really harsh, but the physical performance of the lens was on point, focus was always accurate and it was fast enough. Yesterday I went to Disneyland for the day and brought the Sigma lens, but by the end of the day I wanted to throw it off the top of the Matterhorn. More often than not the autofocus would grab the background instead of the subject, and I'd miss a shot because of it. It's not so much that it's trying to hit the subject and then back focusing or front focusing a little (it did that for a while until Sigma got my money for their USB dock) but that it hunts a lot and then decides I want the trees in focus but the face out of focus. This is like 3 out of 5 attempts.

I'm using the back buttons for focus, the "AF-ON" button for a single point and the "*" button for the whole area (you know, the [     ] selection), then if my subject is moving I'll hold the * and also hold the DOF preview button to switch from one shot to AI servo and track them. With every other lens I have (canon 16-35 F2.8L ii, Canon 24-70 F2.8L, Tamron 150-600mm, and that nifty fifty) this method gets me the shot, but this Sigma lens always acts like I just woke it up from a nap, slightly disoriented, not ready to get to work. When I have a still subject and can set up a shot it works fine. Anything moving and the lens doesn't keep up.

Is this just a _thing_ with this lens? I mean, I know they're plagued with front and back focusing issues, but is it known to perform poorly with focus tracking? I've never fiddled with the first AF menu in the camera's settings (tracking sensitivity, etc) and am wondering if learning about that will help this lens to perform better. If that won't fix it, I guess I'll be selling it for another red ring. Or else I'll keep the lens around for the studio, where I have a model who isn't moving and doesn't have trees around them...


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## andrewdoeshair (Jun 20, 2017)

Also, I realize I posted about a sigma lens in the Canon section. I wasn't sure if this was an issue that could be corrected in my (Canon) camera but if it's the case then I guess Canon users would be the ones to ask. Thanks again and again.


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## Derrel (Jun 20, 2017)

Sounds like my expensive Sigma 180mm f/3.5 EX-APO HSM f/3.5 Macro...it LOVES to back focus...badly...it LOVES to lock on the background and ruin shots!

I dunno...one of thre things with third-party lenses is that the focusing protocols are NOT supplied to the third-party manufacturers by Canon nor Nikon, but are reverse-engineered by Sigma or Tamron or Tokina; my guess is that the way you have the camera set up is part of the issue, with the Sigma lens not responding exactly as it should when the asterisk button and the AF-ON button are programmed to be active.

Perhaps the Sigma lens would work better if another camera setup menu option were used?

Perhaps Canon has tweaked the focusing protocol a bit since they added STM lenses? Regardless, this is not the first time I've heard about or experienced a Sigma with a Sig nificant Mal-function....I own an expensive Sigma that has never worked right with newer Nikons made in the post-D200 and post-D2x era...it was fine on earlier, older camera bodies...


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## jcdeboever (Jun 21, 2017)

I had similar issues with three Sigma lens, two worse than the other. From my understanding, they really are not that good. This was told to me by an older, professional lens repair tech. His opinion was strictly based upon on lens construction and showed me identical models that had vastly different manufacturing flaws, so I learned that their process is not well controlled.

I have since moved on to a different system and do not experience the frustrating missed shots, other than user error stuff. Interestingly, I don't miss many shots using film because I have to slow down and consider every step. My new digital system (Fujifilm) can be set up the same way as my film so no more frustration. I assume with Canon, that using L glass or getting with someone like @zombiesniper, may bear some fruit on lower cost alternatives to the L glass.


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## astroNikon (Jun 21, 2017)

I used to (attempt to) shoot in the old days with film.  I hated the Sigmas from back then.
So I try to avoid them today.  I still hear issues as they have to try and reverse engineer the focusing protocols for Nikon, Canon and what ever other bodies they want to maintain compatibility.

The last Sigma lens I had, a 150-500, the colors were muted and if the lens was left on the camera it would drain the batteries even with the camera off.  Before that the last time I had a Sigma was with a N80; I didn't like it either.

I know they get good reviews but I tend to stick with OEM lenses as often as possible due to color rendition, construction and compatibility.


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## Gary A. (Jun 21, 2017)

I would dump the lens and get something that works for me, everytime I use it ... not against me.  A long time ago I had two Sigma's, a 20mm F1.8 and the 50-500 (Bigma) ... no problem with either lens.


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## SquarePeg (Jun 21, 2017)

Did you buy the lens new?  Is it still under warranty?  May be worth sending it in to have Sigma look at it?


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## andrewdoeshair (Jun 21, 2017)

Dang, thank you everyone. I like what one of you said about shooting film and not having the issue. I guess that would fall under the "learn to live with it" option. I shoot a lot of film with an old Pentax and it's true, taking the time to set up the shot makes all the difference in my keeper rate. This problem is only really a problem if I'm walking and trying to fire off candids of my friends who are also walking. If I stop and say "walk that line" I can get results. I recently bought a manual focus 85mm F1.2 and my keeper rate with that lens is way higher than this one, but I also shoot differently with it, I HAVE TO somewhat plan and fully think about shots.

I stopped into a local camera shop yesterday and tried canon's red ringed 50mm to much disappointment. It doesn't focus any faster (although it's probably way more accurate). I get used to my 24-70 focusing instantly then every other lens feels like it has issues.

I spent a few hours trying to research this issue and I have a better understanding of it now. Initially I thought the problem was that the focusing motor couldn't keep up with where the camera was telling it to focus, but now I'm 90% sure the outer focus points have a front focusing issue while the center point is accurate. If I stick to using the center point I guess I could love the lens again.

I bought the lens barely used from a friend who takes realllly good care of his gear. It was basically new. But that was 3 years ago, so I don't know about the warranty. I think I will have a tech look at it though. The frustrating thing is that it used to be super accurate, or at least I thought it was. For the first year that I was using a full frame this was my only lens, and it was great, but after getting some Canon glass I either started noticing the flaws of the sigma or the flaws only then started to appear. I borrowed a friend's Sigma 35mm Art lens and it was super accurate and produced wayyyy nicer images than the 50mm...

I think I'm just realizing something I should have noticed years ago. It makes sense, but when a lens has enough big heavy glass to have to push around while focusing, it's just not going to get pushed around as quickly. There doesn't exist an F1.2 or F1.4 that focuses super fast, right? When I went into the store to play with the Canon 50mm F1.2L I mentioned I was looking for faster AF and the guy goes "you should try a sigma fifty! It's so fast!" Then after reading around the interwebs I believe I found that canon's 50mm F1.4 is supposed to be on the faster focusing side of wide aperture 50mm lenses...

I'm going to take a step back and a deep breath then have another outing with this lens. Start back to basics and get to know it instead of trying to push the performance and feeling like it's useless. Maybe get out the old test chart and pinpoint exactly what is wrong with it. This makes me feel like I'm losing my mind, but in the past it's had weird issues that seem to go away. For a while I was sure it was misaligned, it lacked contrast and focused on nothing, but then one day it worked fine.


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## paigew (Jun 22, 2017)

Personally, I love the sigma Art series. I have two of their lenses and use them professionally, in extreme circumstances (and even for my school photography work!). They are great. The issue I see is that you are letting the focus system choose your point. You need to toggle or focus and recompose to be sure your images are properly focused.


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## KmH (Jun 22, 2017)

Which Canon 50 mm f/1.8? The older, el cheapo EF-S 18-55mm f/3.5-5.6 IS II that would break into 2 large irreparable pieces if dropped?
Or the newer, 2x more costly, better build version.

Auto focus is not an end-all-to-be-all, and the 5D III's AF module options are so extensive that you may need a college degree to learn how to effectively use AF in the 5D III.

AF has trouble with some scenes because of the way AF works, regardless the lens on the camera.
• Little or no contrast between the subject and the background
• Focus point contains objects at different distance from the camera.
• Subject is dominated by regular geometric patterns
• Focus point contains areas of sharply contrasting brightness.
• Background objects appear larger than the subject. like when a building is in the frame behind the subject.
• The subject contains many fine details - like a field of flowers, a multitude of other small subjects, or a lack of variation in brightness.


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## andrewdoeshair (Jun 23, 2017)

I write this with a little embarrassment, as I have pinpointed the issue and it was really simple. This is probably the third time I've started a thread trying to figure out a problem that ended up only taking a little bit of patient troubleshooting to fix. First I put the lens back on the USB dock to dial in the AF again, and for whatever reason the values I had used the last time I'd done this were no longer getting accurate results. Believe it or not, hitting the button to restore it to factory settings put it pretty much right on target throughout the whole range. When I bought the dock these settings were way off. It's a mystery.

 
 

Ignore that overly warm white balance setting, earlier today I was shooting outside with a blue gel on a speed light to make golden hour look super extra golden.

After the freshly uncalibrated lens was hitting targets accurately I decided to read about the settings on the first screen of the AF settings menu, and when I pulled up the menu I saw that the setting had at some point been switched from "Case 1, versatile multi purpose setting" to "case 2, continue to track subjects ignoring possible obstacles." I swatted the pull chain on a ceiling fan and tracked it swinging back and forth with each case selected. That was it. After switching this setting back, my camera felt normal to me again. I think when it was accidentally set to that second case it wanted to "ignore obstacles" so it was grabbing the more stable background and ignoring my friend's faces, like they were the obstacles.

I just wanted to update this thread with all of that in case anyone else is going through this crap with their Sigma and finds this. I'm going to shoot with it for a few days and check in here with an update as to whether or not it's working properly now. The Sigma really is neat, but it's needed more maintenance than my 1973 Triumph Bonneville to keep it functioning...


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## andrewdoeshair (Jul 12, 2017)

I didn't want to start a whole new thread to ask about this, since it's the same lens we had already been discussing here. Can anyone with a sigma 50mm Art lens tell me if they have issues with lines doubling in the out of focus areas? My other lenses don't do anything like that, but I've been noticing it with the sigma and it's got me wondering if the lens is decentered or something. Look at the edge of the tongue on this shoe, the first picture is the sigma, second picture is a canon 135mm F2L
 
 

Do you see on the sigma (first pic) how some lines are doubled? I've seen it a few times with this lens and only just now thought it might be a symptom of whatever demon might be intermittently possessing this lens. Is that normal for this (or any) lens? I think I'm going to take the thing to get looked at this week.


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## Derrel (Jul 12, 2017)

Double-line bokeh is a well-known issue with some lens designs...It's something that many people are not fond of. I have seen it before. To me, it is unappealing...and your shoe photo sjows two lenses, one that has double-lione bokeh, the other that has a smooth-edge defocus transition.

GOogle "lenses known for double-line bokeh" and you'll fiomnd some links that discuss this issue; double line bokeh is not typically associated with "good bokeh".

One of the things the Sigma ART series has is *exceptionally high test-chart resolving ability*, and the ability to differentiate between closely-spaced LINES on a test-chart...in this internet age, many people buy len ses based on MTF curves, and test-chart resolving figures, and "How many line pairs per millimeter can this lens resolve?"...but test chart scores on lenses do not tell you about the way the pictures actually look.

correction-and-line-appearance-copy.jpg

The double-line bokeh phenomenon is known as _nisen-boke _in Japan.

Bokeh

An excerpt: "*A cropped image that shows the double-line effect (nisen-bokeh) in the blurred background due to overcorrected spherical aberration."
********
*
Guess what...lenses with overcorrected spherical aberration can score HIGHER on simple line-resolving lens sharpness tests! So...there's that incredible tets-chart sharpness that sells lenses to internet-era people, yet...the bokeh suffers.


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## Banjor (Jul 12, 2017)

andrewdoeshair said:


> Do you see on the sigma (first pic) how some lines are doubled? I've seen it a few times with this lens and only just now thought it might be a symptom of whatever demon might be intermittently possessing this lens. Is that normal for this (or any) lens? I think I'm going to take the thing to get looked at this week.



Wow, I certainly do see that. That looks very suspect to me. I don't have that exact lens, but my 30mm ART lens doesn't do anything like that. 

I could imagine how those false "edges" that appear in out of focus areas like the shoe heel could fool contrast detection AF.


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## Derrel (Jul 12, 2017)

Nothing has been "fooled"...the focus on the two shots is very close to the same point...this is a classic example of double-line bokeh rendering...


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