Sigma 50 1.4 art => outer focus points severe front focussing

[nielsgeode]

Yesterday I received my new Sigma 50 art ;D I immediately tested it (on my 5DIII) and found some shocking results. :'(

I have not calibrated this lens yet. Attached are two pictures, both taken at f/1.4. First picture: I used center AF point. Second picture: I used an AF point on the very far left. I contacted Sigma and they say this is not normal.

What are your experiences? Is this likely to be a fault with this single lens or do all sigma 50 art's suffer from this issue?

Thanx!
Niels

 

[leGreve]

Don't you just love how lens companies say that it's normal that their lenses don't work to perfection out of the box.....

You can't even MA this can you? I mean, the adjustment would be pointless the second you change AF spot.

 

[nielsgeode]

As far as I know I can do microadjustment with this lens (haven't checked it), but it would be pointless in this case...

 

[YuengLinger]

I don't like when I post in a forum and am told to read other posts, but in this case, we do have some lengthy, thorough, and insightful discussions about the AF problems some Sigma 50mm Art customers have experienced.

If you read what some of us have been dealing with, you'll understand why I smiled when you said you were "shocked" at the outer-point problems.

Personally, I'll give the lens another chance next year, after Sigma updates the firmware (and makes other tweaks???) and acknowledges that AF issues have been addressed.

I still cannot see the benefit of buying the USB dock when my camera can perform AF micro-adjustments. And, in fact, I have the Sigma 35mm 1.4 Art and it does just great with only in-camera micro-adjustments.

 

[pato]

Transport damage maybe? I mean Sigma already said it's not normal, so it's probably simply broken or a de-centered element.

 

[dlee13]

Maybe Sigma will release a revised version with like they did with their previous 50. The AF issue may still remain but be less severe and less common.

 

[nielsgeode]

Transport damage maybe? I mean Sigma already said it's not normal, so it's probably simply broken or a de-centered element.

If it would be transport damage, you would also expect to see reduced sharpness when you manually focus using live view, right? Because if I do this, the image is perfectly sharp, even wide open. Significantly sharper than my Canon 50mm f/1.4 (which you would expect).

 

[Ruined]

I have never seen such a dramatic variation from AF point to AF point, but apparently that is a known issue with this lens.

There is another thread floating around with many people having autofocus issues with this lens on points other than the center point (there appears more that have problems than those who do not). You might want to call Sigma to see if they have a replacement program, but if you cannot live with this problem I would try another copy from the store you bought it from. If the next copy has the same issue, buy a different make/model lens. If you deal directly with Sigma the store you bought it from will not take back the lens Sigma sends you due to different serial#.

Based on all the reports of problematic AF performance on outer points with this lens, I would guess this is a characteristic of the lens.

 

[YuengLinger]

I have never seen such a dramatic variation from AF point to AF point, but apparently that is a known issue with this lens.

There is another thread floating around with many people having autofocus issues with this lens on points other than the center point (there appears more that have problems than those who do not). You might want to call Sigma to see if they have a replacement program, but if you cannot live with this problem I would try another copy from the store you bought it from. If the next copy has the same issue, buy a different make/model lens. If you deal directly with Sigma the store you bought it from will not take back the lens Sigma sends you due to different serial#.

Based on all the reports of problematic AF performance on outer points with this lens, I would guess this is a characteristic of the lens.

Not a "characteristic" due to design, but a shortcoming of QC, according to the user experiences reported here on CR.

 

[Mika]

I don't think that is an issue with the lens hardware at all. I think this has more to do with lens+body combination in the auto-focus routines. The good news is, firmware update will likely correct this, but you'll have to make noise towards Sigma. There's a similar story of a firmware update improving Sigma's 120-300 considerably. Because of that, I do believe Sigma is going to do something about it.

And come to think of it, Canon EF 50/1.4 isn't reliable with the edge points either when using F/1.4. Heck, it isn't reliable even with the center point!

 

[nielsgeode]

I don't think that is an issue with the lens hardware at all. I think this has more to do with lens+body combination in the auto-focus routines. The good news is, firmware update will likely correct this, but you'll have to make noise towards Sigma. There's a similar story of a firmware update improving Sigma's 120-300 considerably. Because of that, I do believe Sigma is going to do something about it.

And come to think of it, Canon EF 50/1.4 isn't reliable with the edge points either when using F/1.4. Heck, it isn't reliable even with the center point!

I have received a second lens and tested a third copy. They all have the same issue, although the second copy is much sharper. I have contacted Sigma. The say that firmware is nonsense and that the AF-curve is not flat. Sigma can calibrated if you ship the lens to them (in the Netherlands at least). They charge 60 euros ($90) for calibration.

 

[LovePhotography]

Well, I haven't tried this with other lenses, but this certainly seems disturbing... Is this true at other f/stops as well?
Could you post pictures of the second lens trial?
Does this mean that, as of now, this lens should not be on my wish list? The only reason I wanted one is for the sharpness! I have several other lens (less sharp) that cover 50mm (or come close).
I had a Canon 50mm 1.4 that I sold in anticipation of buying this lens, but is the 1.4 a better lens (at 1/3rd the price)?

 

[nielsgeode]

Well, I haven't tried this with other lenses, but this certainly seems disturbing... Is this true at other f/stops as well?
Could you post pictures of the second lens trial?
Does this mean that, as of now, this lens should not be on my wish list? The only reason I wanted one is for the sharpness! I have several other lens (less sharp) that cover 50mm (or come close).
I had a Canon 50mm 1.4 that I sold in anticipation of buying this lens, but is the 1.4 a better lens (at 1/3rd the price)?

I really love the sharpness. As long as you focus using center AF point and then recompose, you're completely safe. Attached is a small test using the Spyder lenscal where you can compare its sharpness at f/1.4 using manual and AF. Both are a crop from the midframe.

I haven't tried it at other f-stops so this I don't know. I would still keep it on the wish list. Apparently Sigma can fix this issue and using only center AF is no problem for portrets (which I use it a lot for).

Just one unavoidable disappointing fact: it has ugly bokeh compared to the canon 50 1.4.