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12-05-2010, 02:59 PM   #1
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How many copies did you try before got your good Sigma 50mm F1.4?

I have tried three Sigma 50mm F1.4 HSM lenses; none of them are good to me.
All three copies have serious front focus issue, especially at wide open. one copy has back focus issue at small aperture.

My question is how many copies you have tried before finally you are satisfied with Sigma?

12-05-2010, 04:15 PM   #2
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I highly doubt Sigma's QC is poor enough to have problems with 3 different lenses, quite possibly from 2 or 3 different production runs. This isn't the 1950's.

Try shooting something real instead of a slanted ruler.
12-05-2010, 06:21 PM   #3
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One.

I had read about the possible focusing issues with the lens, so I made the decision to get my copy from a local store, where I could check out and test the lens out beforehand. Did not have a problem.
12-05-2010, 07:45 PM   #4
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QuoteOriginally posted by brofkand Quote
I highly doubt Sigma's QC is poor enough to have problems with 3 different lenses, quite possibly from 2 or 3 different production runs. This isn't the 1950's.

Try shooting something real instead of a slanted ruler.
I have been shooting real things instead of those table charts. This photo is wide open focusing at a yellow sign aside of the white van in the center of the picture.
You can see the lens is wrongly focused very near front, missing dozens feet.

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12-05-2010, 07:50 PM   #5
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Actually my current copy of Sigma 50mm 1.4 gets FF issue not very serious within a range of 6 feet. It becomes worse beyond 6 feet. Anything 20 feet more is terrible. Does anyone experience this?

QuoteOriginally posted by looktime Quote
I have been shooting real things instead of those table charts. This photo is wide open focusing at a yellow sign aside of the white van in the center of the picture.
You can see the lens is wrongly focused very near front, missing dozens feet.
12-06-2010, 01:21 AM   #6
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QuoteOriginally posted by looktime Quote
I have been shooting real things instead of those table charts. This photo is wide open focusing at a yellow sign aside of the white van in the center of the picture.
You can see the lens is wrongly focused very near front, missing dozens feet.
I think youīre jumping at problems that are not there. What I see from this pic & your statement is that you are judging the AF sensor of the camera to be the same size as the little dot that appears to tell you where itīs focused. The AF sensor is actually considerably larger and has thus detected the bush or fence as the closest object within itīs area to focus on. This is the big downfall of AF - that it does not always focus on what you want it to focus on, it has to guess.

If you want to test for front or back focusing, make 100% sure that thereīs nothing else that the AF system could possibly focus on.
12-06-2010, 02:17 AM   #7
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QuoteOriginally posted by looktime Quote
This photo is wide open focusing at a yellow sign aside of the white van in the center of the picture.
You can see the lens is wrongly focused very near front, missing dozens feet.
You may have wanted to focus on the yellow table, but the flower of the bush (? or small tree?) in the foreground is also in the center AF sensor area, therefore the camera focused on that since it was closer to you. Sorry, this is clearly user error and not lens problem.
12-06-2010, 09:17 AM   #8
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Maybe that picture is not enough to prove it. Here is another one. I focused on the top of third white fence pole. It was focused front a lot.

QuoteOriginally posted by Jonathan Mac Quote
I think youīre jumping at problems that are not there. What I see from this pic & your statement is that you are judging the AF sensor of the camera to be the same size as the little dot that appears to tell you where itīs focused. The AF sensor is actually considerably larger and has thus detected the bush or fence as the closest object within itīs area to focus on. This is the big downfall of AF - that it does not always focus on what you want it to focus on, it has to guess.

If you want to test for front or back focusing, make 100% sure that thereīs nothing else that the AF system could possibly focus on.


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12-06-2010, 09:27 AM   #9
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Here is one more. Focusing at double solid yellow lines on the road but shift front to curb area.
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