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Archive 2008 · The Sigma 50mm f1.4 AF Problem Thread

Jman13
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p.2 #1 · p.2 #1 · The Sigma 50mm f1.4 AF Problem Thread

Out of curiosity...why would you want to focus stopped down? I've never had a desired to stop down to f/8 and focus at that aperture or anything. The only times I'll focus stopped down is on larger aperture alternative lenses, where I may focus my Takumar 50 f/1.4 at f/2 just to avoid the aperture action.

Oct 21, 2008 at 11:37 AM

ovredal73
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p.2 #2 · p.2 #2 · The Sigma 50mm f1.4 AF Problem Thread

ovredal73 wrote:
I tried the Sigma on a 350D today and it focuses fine there. So now I have actually turned in my 5D for AF repair, to make sure that is not the problem. Maybe the FFcameras/5D are more sensitive to a weak AF precision level on the Sigma? Or does that sound like science fiction?

To clearify why I turned in the camera for possible AF repair before returning the lens - I found my 85L which I havent used in a year, to also (suddenly) have severe backfocus issues on the 5D, while not having it on the 350D. And to completely eliminate any question to the functioning on my 5D. In the repair shop log the camera is set to have AF adjustment done tomorrow, whatever that entails.

Could exclusively using old exotic MF lenses over the last year screw up my camera´s AF somehow?

Oct 21, 2008 at 11:40 AM

ovredal73
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p.2 #3 · p.2 #3 · The Sigma 50mm f1.4 AF Problem Thread

thrice wrote:
not science fiction, both of my faulty copies were fine on the 40D. I believe Sigma failed at reverse engineering canon's AF algorithm for a 50/1.4 lens on full frame.

That is how I feel as well. However if my 85L also continues to focus badly, there is either something wrong with both those lenses or with the camera. So the only question now, is the performance of my 5D. Then I will start blaming the lens again.

André

Oct 21, 2008 at 11:45 AM

Jman13
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p.2 #4 · p.2 #4 · The Sigma 50mm f1.4 AF Problem Thread

Andre - make sure you're not testing under fluorescent lights. There are several of us (me included) who have bodies that backfocus under fluorescents with fast lenses (My 30 f/1.4 and 85 f/1.2 do it), but are dead on accurate under any other light.

Oct 21, 2008 at 11:57 AM

Andi Dietrich
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p.2 #5 · p.2 #5 · The Sigma 50mm f1.4 AF Problem Thread

Sorry Jonas, did not visit the link, just read what you folks have to say here.

Jman, only to see if there was any focus shift. There is an articel on focus shift on vanwalree.com > spherical

Oct 21, 2008 at 12:11 PM

ovredal73
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p.2 #6 · p.2 #6 · The Sigma 50mm f1.4 AF Problem Thread

Jordan, I have tested in natural light (indoor daylight shade).

Oct 21, 2008 at 12:54 PM

positron
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p.2 #7 · p.2 #7 · The Sigma 50mm f1.4 AF Problem Thread

has anyone seen any problem on a 1D camera?

Oct 21, 2008 at 01:27 PM

ovredal73
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p.2 #8 · p.2 #8 · The Sigma 50mm f1.4 AF Problem Thread

Greetings from the OP.

I have now had Canon adjust my 5D to factory specs, using their own in house ref lens (whatever that is).
The Sigma went from completely out at mostly any distance to display spot-on focus at every distance.
I realized this possibility when suddenly my 85L was as out as the Sigma. I havent used the 85L much the last couple of years, since I started shooting with alts.

I will post more on this later, including test images, to show what happened. It is quite amazing how way out my 5D was, even the technician was somewhat surprised by it. I wonder if all my alt lens use could be to blame for this. Anyway, he said now the camera is better than new

And my 1006xxx Sigma is now a complete babe on my 5D

EDIT: That is, under less ecstatic scrutinization, it now front focuses a bit. I will turn the lens in at the Sigma dealer tomorrow and have it adjusted. Then, I think it should all be great...

Oct 22, 2008 at 07:34 AM

trumpet_guy
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p.2 #9 · p.2 #9 · The Sigma 50mm f1.4 AF Problem Thread

ovredal73,

When you get a chance, try the Sigma on your 5D at wide open and distant focus. Do you see any
backfocus?

Very good news from you here.

Oct 22, 2008 at 03:20 PM

ovredal73
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p.2 #10 · p.2 #10 · The Sigma 50mm f1.4 AF Problem Thread

Dear Tim, that is exactly it. I have been doing tests with no less than 4 copies of this lens, all to horrific back focus at distant subjects. Now, after having Canon tune my 5D, the lens is actually front focusing a tad. No back focus anymore. Of course wide open with distant focus

Oct 22, 2008 at 04:39 PM

Jonas B
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p.2 #11 · p.2 #11 · The Sigma 50mm f1.4 AF Problem Thread

ovredal73 wrote:
Now, after having Canon tune my 5D, the lens is actually front focusing a tad. No back focus anymore. Of course wide open with distant focus

Good news indeed.
Please just confirm this: You now have a Siggy50, serial 1006***, a 5D and you get a consistent front focus, whatever the shooting distance is. Do I get it right?

Oct 22, 2008 at 06:20 PM

AGeoJO
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p.2 #12 · p.2 #12 · The Sigma 50mm f1.4 AF Problem Thread

ovredal73 wrote:
Some more points:

1. Are there any problems with Nikons or is this a Canon-only issue?

Is this really a Canon-only issue? Has that been confirmed?

Oct 22, 2008 at 06:34 PM

theSuede
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p.2 #13 · p.2 #13 · The Sigma 50mm f1.4 AF Problem Thread

That might be hard to "confirm" in the exact meaning of the word - but judging by other comments on the net and return-rates to my local pro stores (as reported by the store personnel), mostly EF-mounts is affected. The return rates with F and K mounts seem to be at normalcy regarding Sigma lenses. This nowadays actually means a bit lower than some "L" optics... :/

Oct 22, 2008 at 07:05 PM

Drew_Persson
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p.2 #14 · p.2 #14 · The Sigma 50mm f1.4 AF Problem Thread

Just received my copy, serial 1007xxx.

Some 100% crop focus test shots using 1Ds2:

At 25 feet (red arrow pointing at focus target)
http://www.phototurbo.com/temp/50sigma25ft.jpg

At 5 feet
http://www.phototurbo.com/temp/50sigma5ft.jpg

Disregard exposure, which was +1EV.

Focus seems right on the money! Definitely need your focus target to stand out against the background though, initially I put the target on a cinder block seam and the AF picked up the seam instead of the target.

Note the purple fringing before focus plane and green after, to be expected I suppose with CA of about 1/3 pixel. Very nice lens though, well-built and solid, good match for the 1Ds2. Just need to check out the bokeh now!

Oct 22, 2008 at 07:20 PM

ovredal73
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p.2 #15 · p.2 #15 · The Sigma 50mm f1.4 AF Problem Thread

Jonas B wrote:
Good news indeed.
Please just confirm this: You now have a Siggy50, serial 1006***, a 5D and you get a consistent front focus, whatever the shooting distance is. Do I get it right?

Yes, that is correct. But I think the front focus is quite a simple adjustment. I will turn it in today.

Oct 23, 2008 at 01:14 AM

ovredal73
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p.2 #16 · p.2 #16 · The Sigma 50mm f1.4 AF Problem Thread

Drew_Persson wrote:
Just received my copy, serial 1007xxx.

Some 100% crop focus test shots using 1Ds2:

Disregard exposure, which was +1EV.

Focus seems right on the money! Definitely need your focus target to stand out against the background though, initially I put the target on a cinder block seam and the AF picked up the seam instead of the target.

Note the purple fringing before focus plane and green after, to be expected I suppose with CA of about 1/3 pixel. Very nice lens though, well-built and solid, good match for the 1Ds2. Just need to check out the bokeh now!

And the bokeh is nice too, now that it is in the right place

Thanks for the test images. Good news for FF users.

Oct 23, 2008 at 01:16 AM

Drew_Persson
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p.2 #17 · p.2 #17 · The Sigma 50mm f1.4 AF Problem Thread

Look on page 22 of the Marmite Bokeh thread for a quick bokeh shot with this lens, don't want to double-post.

Oct 23, 2008 at 11:45 AM

bonyari
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p.2 #18 · p.2 #18 · The Sigma 50mm f1.4 AF Problem Thread

I just tested my copy of the lens and found that at short distance, it front-focuses. And at large distance, it back-focuses (quite a bit).

For those who are experienced with getting the lens adjusted, is this an easy to fix problem? I mean if I turn it into Sigma, will they be able to get it spot on? I have about 2 weeks left to return the lens to the dealer, so I'm a bit anxious and might just return it to the dealer.

Sep 27, 2009 at 11:28 PM

trumpet_guy
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p.2 #19 · p.2 #19 · The Sigma 50mm f1.4 AF Problem Thread

The short answer is: No, there is no guarantee they can fix it.
Mine has the same problem. I sent it to Sigma in New York.
I also sent them my 5D so that they could adjust it to my specific
body (which works fine with other fast lenses). The supervisor
spent time with the tech on this. He called me and talked with me
and said that while they couldn't get it perfect, he felt I would
be happy with it.

It came back with the same issue -- no improvement, as far as I can tell.
Mind you, it's not a severe problem as it is, but it is significant. And it
means I cannot trust AF at long distances if I'm shooting at large aperture.
This would be no problem if modern bodies had brighter viewfinders, but
even the relatively good 5D viewfinder does not make precise focus easy
to achieve.

Bottom line -- if you are not satisfied with the copy you have, send it back.
Don't mess with Sigma repair.

Sep 28, 2009 at 12:15 AM

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