I think this qualifies as a bad copy? My lens saga....

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clicktor

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Objective: Wanted an upgrade from my kit lens with constant f/2.8 if possible. looked at the Tamron 17-50mm f/2.8 and Sigma 18-50mm macro f/2.8. Decided for a few reasons to go with the Sigma. I managed to get one off of this forum for a good price. Job done I thought...
On first inspection it had a hair and some dust inside the lens behind one of the elements. Fair enough I thought, I'll live with that as it won't affect the image and it's second hand. Then I thought it was soft and front focused, but later found that my Camera needed adjusting. Finally I have had some time to fix the cam and retest. I was still adament that it was soft down the left side, but the seller would not take it back or provide a receipt for repair. (Please do not think I am turning this into "have a pop at the seller", rather, I am just stating facts).
Since this is my first venture to 3rd party lenses and hearing of the QC concerns of others, I wasn't sure if I was being picky or if it genuinely was soft. I decided to purchase at significant cost to myself a new lens so that I had some come back/warranty if need be. I kept it UK to avoid return issues.
Well...the new Sigma 18-50mm EX DC Macro f/2.8 turned up and I shot various tests to compare. They say a picture speaks a thousand words so....


Old Bad lens:


badR.jpg


bad100.jpg



Good New lens:


goodR.jpg


good100.jpg



Ok, so the settings between the shots had a slightly higher ISO and hence shutter speed on the "good" lens so will look a bit brighter. But since both had plenty high enough shutter speed to avoid camera shake, this was all about just demonstrating even sharpness across the frame. These are both wide open at f/2.8. The 100% crop shots are of the top left hand corner of each image. They are roughly the same focal length (38 and 40mm). JPEG Compression has made the wall look a bit distorted but you get the idea.
 
They work now.
 
I know I've seen a similar thing.

I had a stellar Tamron 28-75, so another TP member (Hello Jonathan!) came over to mine and we tried his.

His lens was like your "bad copy" - I'm not really fond of the term bad copy though, because that implies a QC problem.

However you have no idea how a used lenses was handled - with optics like the above, I would expect a drop or knock.I doubt it left Sigma like that.

If in doubt ask for 100% crops before buying used.
 
What do you want us to say??? yes the good lens is better?? ps, if you are going to test sharpness you really should tripod, mirror lock up and shutter cable release it, and try a range of f stops as lenses are always going to be a bit softer fully wide open.
 
First pic is clearly out of focus. Miles out, all over. Even if a lens is dodgy it will still be sharp somewhere across the frame unless something very strange has happened. Is this really as sharp as you could get it?

If so, that's not mere 'bad copy' it's faulty. Not just misaligned somewhere in manufacture, but assembled wrongly. Has anyone had it apart?
 
Apparently, sigma are notorious for QC issues, with several people having to send back up to 3 lenses before they got a good copy. This could have been one of those bad 'uns.

Whoever sold this to you either knew exactly what was going on or just thought that this was the best this particular type of lens was going to be and innocently passed it on. Either way, hard to prove.
 
It's not out of focus though, or at least not "user error". I see responses like that so often when someone complains about a lens being soft. I took various test photos and this is just one example. The left side is much worse than the right. I think it had been dropped yes, but who knows.
 
HoppyUK said:
First pic is clearly out of focus. Miles out, all over. Even if a lens is dodgy it will still be sharp somewhere across the frame unless something very strange has happened. Is this really as sharp as you could get it?

If so, that's not mere 'bad copy' it's faulty. Not just misaligned somewhere in manufacture, but assembled wrongly. Has anyone had it apart?
Click to expand...

Hey hoppy, I agree with you entirely. That was the whole point in this test. I don't really care for if it was a little soft 100% crop wide open, but the left side is FAR softer than the right which would normally indicate a miss alignment issue I gather. Anyway, the new lens I absolutely cannot replicate these issues and it's perfect out of the box in my opinion.


nuttyboy78 said:
Apparently, sigma are notorious for QC issues, with several people having to send back up to 3 lenses before they got a good copy. This could have been one of those bad 'uns.

Whoever sold this to you either knew exactly what was going on or just thought that this was the best this particular type of lens was going to be and innocently passed it on. Either way, hard to prove.
Click to expand...

The guy who sold it to me is a regular seller on here with 100% feedback and a fair amount of it, which is why I bought with confidence.

Hawker said:
What do you want us to say??? yes the good lens is better?? ps, if you are going to test sharpness you really should tripod, mirror lock up and shutter cable release it, and try a range of f stops as lenses are always going to be a bit softer fully wide open.
Click to expand...


Again I agree, and I would normally do this, but when the results show so easily with what I would consider "normal" usage I just posted a quick test I did.
 
I tested a pair of Sigma 18-50 f/2.8 EX Macro and one was noticable worse than the other.

One was excellent, one one de-focused and hazy. I may still have the test shots. The serials numbers were only 100 apart.
 
clicktor said:
Hey hoppy, I agree with you entirely. That was the whole point in this test. I don't really care for if it was a little soft 100% crop wide open, but the left side is FAR softer than the right which would normally indicate a miss alignment issue I gather. Anyway, the new lens I absolutely cannot replicate these issues and it's perfect out of the box in my opinion.
Click to expand...

Yeah, the right side is sharper. It does look like a serious case of misalignment.
 
The first thing I have to say is YOU need to take both photos with same settings
First one is
Original Date/Time = 2009:09:29 06:26:39
# Exposure Time (1 / Shutter Speed) = 1/250 second ===> 0.004 second
# Lens F-Number / F-Stop = 28/10 ===> ƒ/2.8
# Exposure Program = manual control (1)
# ISO Speed Ratings = 800
# Focal Length = 40/1 mm ===> 40 mm

Second one is
Original Date/Time = 2009:10:22 16:33:33
# Exposure Time (1 / Shutter Speed) = 1/400 second ===> 0.0025 second
# Lens F-Number / F-Stop = 28/10 ===> ƒ/2.8
# Exposure Program = aperture priority (3)
Aperture = ƒ/2.8
# ISO Speed Ratings = 1600
# Focal Length = 37/1 mm ===> 37 mm
Was it on a tripod with mirow lock up and remote fired?
I see an hour between shots? if I was testing two lens I have it set up on tripod remote fit one lens set shoot change lens same settings and shoot
 
I once bought a used Sigma 24-70 2.8 that I found incredibly soft unless stopped to f8...so pretty pointless! Luckily the seller let me return it, stating it was very sharp for him! Baring in mind I was using it with a D200 that didn't have AF adjust, that may well have been the case. I also tried in the shop a 18-50 Sigma 2.8 that also front focussed a little. I've now made up my mind that if I ever purchase a 3rd party lens, it will be tested by me in the shop prior to purchase - however I would trust purchasing a used Nikon lens.
 
I agree with others that to be 100% sure this is a bad copy you need to put it on a tripod, mirror lockup, and shoot the same scene preferably with a remote release at 2.8 4.0 5.6 8.0 11 and 16.

Make sure you get a focus confirmation beep before you release the shutter.

Then compare the shots at the same apertures.

However, from your informal test it does look like a bad copy. I've had this before but I bought new and sent the lens back to WarehouseExpress and they sent me another perfectly sharp copy of the Sigma 30 f/1.4

If a more controlled test confirms the issue, send an email to Sigma Service [service@sigma-imaging-uk.com] and ask them what they can do to correct the problem and how much it would cost.
 
Chaz Photos said:
Was it on a tripod with mirow lock up and remote fired?
Click to expand...

maarten.dhaese said:
I agree with others that to be 100% sure this is a bad copy you need to put it on a tripod, mirror lockup, and shoot the same scene preferably with a remote release at 2.8 4.0 5.6 8.0 11 and 16.
Click to expand...

While this is hardly a strictly controlled test, I don't see any reason why you need to bother with a tripod, mirror lock-up and remote release. Or to shoot at a range of f/numbers - lowest f/number is all you need. And irrelgular corner sharpness is all you need to look at.

Hand held is fine so long as the shutter speed is high enough, which it is. Being square to the target is also important, but even more important is to get the focus as accurate as possible. Which is why a distant subject is better, as there is less chance of error at infinity, or field curvature.

Brick walls are a poor test target. Shooting newspapers, the other popular subject, is even worse. If you're looking to check sharpness, anything two-dimensional and shot close up is likely to be unreliable, especially with a wide lens.
 
nuttyboy78 said:
Apparently, sigma are notorious for QC issues, with several people having to send back up to 3 lenses before they got a good copy.
Click to expand...

So out of the thousands of lenses they sell, have sold, several complaints makes them notoriously bad....:suspect:

With Sigma being so bad and having such lousy quality control, I wonder how they are still in business? I mean every nikon or canon lens ever made has never had a problem,have they?

Sigma/Tamron/Tokina/whoever are cheaper than Canon or Nikon, so don`t expect the same level of build quality, you will generally be disappointed.

Happy owner of four Sigma lenses, no probs with any of them.........:thumbs:
 
Cheers guys. I also tried car number plates from a distance and whilst less obvious, the left was also weaker again. Yes there was a month difference between the shots, and as stated slightly higher ISO and shutter on one of them, but that's not the point here. I was testing even sharpness across the frame with a quick test. If it is showing as obviously as that then clearly a problem I feel.
On the subject of Canon lenses having faults or "bad copies" of course it happens. Just much less often.
 
nuttyboy78 said:
Apparently, sigma are notorious for QC issues, with several people having to send back up to 3 lenses before they got a good copy. This could have been one of those bad 'uns.
Click to expand...

I find a lot of people are "dud magnets", and frankly if they are really going through that many, then often its a user or body problem and not the lens.

On the flip side.. the Sigma 12-24 is almost impossible to buy without getting a de-centered one.

I also find a lot of brand fanatics (usually those who boast about how many "L" lens they have (with the L in red off course :lol:), will always have problems with 3rd party lenses, and frankly the real problem is that the lens doesn't say Canon or Nikon on the lens barrel ;)
 
Well I have owned and/or used for significant periods in the past several Canon lenses and every time I have never had an issue. I have only ever had a problem with a 50mm f/1.8 that front focused slightly, and a friend of mine had a Canon 70-200 f/4 that had focus issues too. Otherwise everything fine. This is my first time I have ever shot with a 3rd party lens and typically I have problems. I also shared the same opinion that it was generally a bunch of over analytical scaremongers, but I think the QC issues are well founded based on this experience.
Oh well, I have a Sigma that works fine now anyway and it's a great lens!
 
Well IMHO your issue is not a QC issue, its because its been dropped or abused. Can't blame Sigma for that really.

Assuming you tested correctly then I don't believe it left the factory like that.

I also suspect a lot of "duds" gets re-cycled - ie returned to the shop / retailer and resold.

I don't think Sigma would have stayed in business for 25 years+ if the QC was a bad as its sometimes stated. The truth is probably somewhere in between.
 
I have the Sigma 18-50 and a 24-70 (from Andy), both are very sharp on my D300, in fact I love em, particularly the latter. My 10-20 too is the same, and I'm not aware of any decentrering issues on my 12-24 but I am going off experience in the field rather than any testing charts. It would be great to have all Nikon lenses but can't afford it and am happy with my 3rd party lenses.

My 18-50 is definately good at 2.8 and at f4 it's really nice, the example above is definately a problem lens. Rather than write it off may be worth paying a little to get it repaired and set up properly?
 
puddleduck said:
I find a lot of people are "dud magnets", and frankly if they are really going through that many, then often its a user or body problem and not the lens.

On the flip side.. the Sigma 12-24 is almost impossible to buy without getting a de-centered one.

I also find a lot of brand fanatics (usually those who boast about how many "L" lens they have (with the L in red off course :lol:), will always have problems with 3rd party lenses, and frankly the real problem is that the lens doesn't say Canon or Nikon on the lens barrel ;)
Click to expand...

Well I've no end of problems with Sigma and I think I can handle a camera reasonably well. Two 120-300 with back focus and slow focus issues, the same with a 300mm 2.8 I had as well. A 10-20mm that was as about as much use a door stop and a new 100-300 that was delivered new from a UK dealer with a dead earwig inside:D

Suffice to say i now own Nikon lens and have never had any issues:thumbs:
 
gpa said:
and a new 100-300 that was delivered new from a UK dealer with a dead earwig inside:D

Suffice to say i now own Nikon lens and have never had any issues:thumbs:
Click to expand...

Do you really believe that Sigma shipped a lens with an earwig inside?

Or is it not more likely the lens was store in a room somewhere with the rear lens cap not fitted? Rear elements move in and out and are not sealed, its very easy for things to get inside, if not capped.

I think Occums razor applies here - and also gives truth to my dud magnet post earlier :D
 
puddleduck said:
Do you really believe that Sigma shipped a lens with an earwig inside?

Or is it not more likely the lens was store in a room somewhere with the rear lens cap not fitted? Rear elements move in and out and are not sealed, its very easy for things to get inside, if not capped.

I think Occums razor applies here - and also gives truth to my dud magnet post earlier :D
Click to expand...

You tell me LOL especially as it was a sealed box. I can only report along with the other issues I have found. I am not telling anyone to not buy Sigma, only give my opinion as to my experience.
 
neil_g said:
the boxes arent air tight are they though, earwigs are pesky little things. theres one that lives in a minute hole in my bedroom window sill lol
Click to expand...

No your right, I guess it was the nail in the coffin so to speak.
 
puddleduck said:
I find a lot of people are "dud magnets", and frankly if they are really going through that many, then often its a user or body problem and not the lens.

On the flip side.. the Sigma 12-24 is almost impossible to buy without getting a de-centered one.

I also find a lot of brand fanatics (usually those who boast about how many "L" lens they have (with the L in red off course :lol:), will always have problems with 3rd party lenses, and frankly the real problem is that the lens doesn't say Canon or Nikon on the lens barrel ;)
Click to expand...

Um no.
I had a problem with a Sigma 24-70 and had to return it, the replacement was much sharper. And it was defo. a QC problem.

And that was before I had an L(:D) lens, & before I could really use a camera.;)

Spence
 
puddleduck said:
I find a lot of people are "dud magnets", and frankly if they are really going through that many, then often its a user or body problem and not the lens.

On the flip side.. the Sigma 12-24 is almost impossible to buy without getting a de-centered one.

I also find a lot of brand fanatics (usually those who boast about how many "L" lens they have (with the L in red off course :lol:), will always have problems with 3rd party lenses, and frankly the real problem is that the lens doesn't say Canon or Nikon on the lens barrel ;)
Click to expand...

puddleduck said:
Well IMHO your issue is not a QC issue, its because its been dropped or abused. Can't blame Sigma for that really.

Assuming you tested correctly then I don't believe it left the factory like that.

I also suspect a lot of "duds" gets re-cycled - ie returned to the shop / retailer and resold.

I don't think Sigma would have stayed in business for 25 years+ if the QC was a bad as its sometimes stated. The truth is probably somewhere in between.
Click to expand...

I agree :thumbs:
 
Took delivery yesterday of a Sigma 18-50 OS HSM and its bloody awful

Compared it with my Sigma 17-70 and can't believe just how poor it is

Going back for a refund, so looks like I have just been unlucky, can't be bothered trying another sample though

My first experience of a wrong'un, must say i'm a bit disappointed and through no fault of my own out of pocket with postage costs
 
Sigma 24-60mm DG EX f2.8
Sigma 50mm DG EX Macro f2.8
Sigma DC EX 50-150mm HSM II f2.8
Sigma 70-200mm APO EX f2.8
Sigma 100-300mm DG EX f4
Sigma 50-500mm DG EX Bigma
Sigma DG EX 1.4x & 2x Teleconverters

Absolutely no problems with any of them apart from a sticky aperture lever on the 1.4x TC caused by my son knocking a cup of coffee over it.

£80 for Sigma to fix that. :bang:
 
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