Strange front-focusing problem with Sigma 35/1.4
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badlydrawnboy
Registered: Mar 19, 2006
Total Posts: 1856
Country: United States

It's hard to figure out what's going on. Since I've had problems with several different lenses, I'm tempted to think it's the camera. Another reason I lean in that direction is that I had a 5D classic and 5DII before the 5D3, and I remember noticing that pictures didn't seem as sharp with the 5D3 as with the other two when I first got it.

On the other hand, while the 24-70 does seem a little soft to me wide open, it appears to be hitting focus most of the time. Doesn't that suggest the problem isn't with the camera? It's hard to believe I could be so unlucky as to have issues with 6-7 lenses, but then again those lenses have been:
Sigma 50/1.4 (2 copies; both returned)
Sigma 85/1.4 (2 copies; both returned)
Canon 50/1.4 (sent to Canon for service; turned out to have a broken assembly and was replaced)
Canon 50/1.2 (sent to Canon for calibration with 5D3; focused accurately after that, but I ended up selling it.)
Sigma 35/1.4 (appears to be front-focusing consistently and significantly)

I've yet to hear anyone else complain of AF problems with the Sigma 35. Every review glows about it, and Roger at LensRentals has tested several copies that have all been fine. Just my luck to get one that isn't (if that's the case).



Yohan Pamudji
Registered: Jul 17, 2003
Total Posts: 1407
Country: United States

Sounding a lot like the 5DIII is the culprit.



Lord Gnome
Registered: Nov 23, 2012
Total Posts: 4
Country: United Kingdom

badlydrawnboy -my first copy of this lens was also front focusing on a 5D3 by quite a margin. Unfortunately that margin was not consistent and the MFA required seemed to vary between +10 and +20. I exchanged it and the new copy is perfect and living up to the hype.

This may or may not be relevant to you but I thought it would be good for you to know that it might not be the camera.

All the best,

LG



badlydrawnboy
Registered: Mar 19, 2006
Total Posts: 1856
Country: United States

Thanks LG. After shooting more with the 24-70 II, I can safely say that if it is the camera that's off, it's only by a small amount. The 24-70 is hitting focus more often than not, even though it does seem a bit softer wide open than I expected. The 35/1.4, on the other hand, is front-focusing consistently beyond what can be compensated for with micro-adjustment. So back to B&H it goes. Sigh. Just my luck... the vast majority of people who've bought the 35/1.4 seem to have goteen good copies. I'm now 0 for 5 with Sigma: 2 bad copies of 50/1.4, 2 bad copies of 85/1.4, one bad copy of 35/1.4. Let's hope I don't stretch it to 0 for 6.



Gunzorro
Registered: Aug 28, 2010
Total Posts: 6830
Country: United States

It may be your body, and your plan to send to Canon is a good one. But as someone else said, this one reason I avoid aftermarket lenses (and am even becoming slightly disenchanted with Alt lenses) -- I can't just package up the items in question and send to Canon for assessment and solving. We talk about some advantages of the Nikon/Sony sensors etc, but I love Canon CPS and having that technical back-up waiting for me.

I hope it works out and you are confident in your gear again.



badlydrawnboy
Registered: Mar 19, 2006
Total Posts: 1856
Country: United States

Gunzorro wrote:
I hope it works out and you are confident in your gear again.


That's what it really comes down to, isn't it? It sucks not to have confidence in my gear. And I hear you about the ability to send the stuff into Canon for calibration. I'm beginning to see how valuable that is.

I'll probably give the 35/1.4 one more chance. But at this point, I'm definitely leaning toward an 85/1.8, 100/2 or 85L instead of the Sigma 85/1.4. With my record with Sigma (0 for 5), I'm just losing patience.



Gunzorro
Registered: Aug 28, 2010
Total Posts: 6830
Country: United States

You apparently don't have another Canon body to test the lens on?

It is always challenging to get all your gear calibrated and working correctly, the more so with more gear. But when it is successful, it's like the stars have aligned and you can't fail to good work.



bigfredtn
Registered: Dec 30, 2003
Total Posts: 382
Country: United States

Gunzorro wrote:
You apparently don't have another Canon body to test the lens on?





badlydrawnboy
Registered: Mar 19, 2006
Total Posts: 1856
Country: United States

No, unfortunately I don't have another body to test the lenses on.

Here are a few more 100% crops at f/2.8 with the 24-70 II (with some capture sharpening applied in LR). I'm still going to send my 5D3 into Canon because the AF seems not quite right, but the 24-70 is far, far better than the 35/1.4. Regardless of whether there's a slight issue with the body, it's now clear that the Sigma 35 is way off.





badlydrawnboy
Registered: Mar 19, 2006
Total Posts: 1856
Country: United States

Well, for what it's worth I think my 5D3's AF is probably fine, and the issue was entirely with the Sigma 35/1.4. I just got my Canon 50/1.4 back from Canon Service, and they acknowledged that the lens assembly was broken and replaced it. That was one of the other lenses I was having issues with, in addition to a Sigma 85/1.4 which has already been returned.

Here are a few 100% crops from the 50/1.4 @f/2.8. Again, just some light capture sharpening applied in LR4.






badlydrawnboy
Registered: Mar 19, 2006
Total Posts: 1856
Country: United States

I must be a glutton for punishment. I've now had to return 5 copies of different Sigma lenses due to AF issues (2x 50/1.4, 2x 85/1.4 and 1x 35/1.4). But I will try one more copy of the 35/1.4 and 85/1.4 before throwing in the towel. Just ordered from B&H.



Ernie Aubert
Registered: Apr 19, 2007
Total Posts: 4534
Country: United States

To employ a British turn of phrase, do please let us know how the new copies are.



scalesusa
Registered: Sep 02, 2008
Total Posts: 2485
Country: United States

I just pass up Sigma lenses. Lots of hype out there, but I've had too many bad sigma lenses to believe any of it. Its easy to pay $$$ for a lens and brag about how good the images are, but I've had a 70+ % poor rate.



badlydrawnboy
Registered: Mar 19, 2006
Total Posts: 1856
Country: United States

scalesusa wrote:
I just pass up Sigma lenses. Lots of hype out there, but I've had too many bad sigma lenses to believe any of it. Its easy to pay $$$ for a lens and brag about how good the images are, but I've had a 70+ % poor rate.


I know what you mean. It's frustrating, because I know there are good copies out there, and when they're good they're often better than their equivalents in Canon mount (35/1.4 & 50/1.4 the 85/1.4 is not better than the 85L, but at half the price it's a pretty good alternative).

But I am literally 0 for 5 with Sigma so far. If I go 0 for 7 with these next two copies, it'll be pretty hard to justify another Sigma purchase.



artyH
Registered: May 29, 2011
Total Posts: 14
Country: N/A

Your Canon lenses look great to me. No problem there, and they are almost "too sharp" for portraits of adults.
I have a Sigma 50 F2.8 macro lens and AF is fine on it. I have heard few complaints about AF on macro lenses, but that is not surprising. AF is much less of a problem for an F 2.8 lens, than an F1.4 lens. Most people don't use AF for much of their macro shooting, anyway.



badlydrawnboy
Registered: Mar 19, 2006
Total Posts: 1856
Country: United States

Ernie Aubert wrote:
To employ a British turn of phrase, do please let us know how the new copies are.


Will do. They arrive on Friday and I intend to put them through their paces over the weekend. It won't take long to find out if the new copy is front-focusing as bad as the last copy.

Interesting thing is that FoCal returned a -1 AFMA when I calibrated the Sigma 35/1.4, which is clearly front-focusing beyond what can even be corrected with MA. I wonder if the difference is that I calibrated at 50x focal length, but the front-focused shots were taken at 3 feet.



Ernie Aubert
Registered: Apr 19, 2007
Total Posts: 4534
Country: United States

With the lens that you've now sent back, did you try ignoring what Focal said and attempt the manual, trial-and-error method of accomplishing MA? Someone else reported (in this thread? I don't remember) bogus behavior from Focal. I'd be interested to know how you fare without employing Focal...



badlydrawnboy
Registered: Mar 19, 2006
Total Posts: 1856
Country: United States

Ernie Aubert wrote:
With the lens that you've now sent back, did you try ignoring what Focal said and attempt the manual, trial-and-error method of accomplishing MA? Someone else reported (in this thread? I don't remember) bogus behavior from Focal. I'd be interested to know how you fare without employing Focal...


Yes, I dialed a +20 in and that helped. But, the front-focus was too extreme to be corrected with even +20, and second, it didn't seem to front-focus much at all at longer distances, so a +20 actually made it back-focus in those situations. That's probably why FoCal was returning a -1. I should have tried calibrating with FoCal at 3 feet to see if it picked up on the front-focus, but since I already knew I was returning it I figured there wan't much point.



Ernie Aubert
Registered: Apr 19, 2007
Total Posts: 4534
Country: United States

Then yes, that sure sounds like a lens issue, all right. I hope your next copy works out.



badlydrawnboy
Registered: Mar 19, 2006
Total Posts: 1856
Country: United States

Well, I got the next copy today along with another copy of the 85/1.4. This is so confusing. I pulled the 35/1.4 out and snapped a few test shots of my wife, focusing on her eye. Nothing scientific; just normal usage. Again, it seemed to be front-focusing significantly. The tip of her nose was in focus, but her eye was blurry. Snapped several shots like this and got the same result. These were taken at a close working distance, i.e. 2-3 feet.

So I thought, ah, yes, the problem is with the camera after all. To confirm I put the new 85/1.4 on and took a few test shots. Nailed focus and very sharp at f/1.4.

Is it possible that the camera could have an AF problem that shows up more with some lenses more than others? Because even with Sigma's reputation, I find it hard to believe that I have been this unlucky with their lenses. Out of 7 copies total (2x 35mm, 2x 50mm and 3x 85mm) with this camera body, only one (my most recent copy of the 85) has been good. Not to mention the fact that Roger from LensRentals has tested multiple copies of the Sigma 35 and they've all been accurate with AF.

I think at this point I'm just going to send the 5D3 in to Canon. If I don't, I will always doubt.

Not sure if I should once again return the Sigma 35, or just send it in to Sigma with my 5D3 once I get it back from Canon.



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