Sigma servicing and possible recalibrating

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mumrar

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Matt
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After a lot of time (owned since May 2008) I decided to do a lot of real world tests of my Sigma 10-20mm to try (on an EOS 450D) and determine if there were any problems with it, or if it was user error. So, with my camera setup on a nice open landscape upon tripod I took a series of shots at f/9, focussing firstly through the viewfinder on centre-point AF (A bunch of trees).

Then I did the same shots except using the AF on live view at the same area of the picture.

Lastly, I used zoom-in on live view to manually focus the scene how I would choose.

I don't need the images peeped at, but what I learnt was that in traditional AF it is always wrong when trying to infinity focus, and the resulting images are very soft. Using live views AF it gets a lot sharper, but things in the centre are not what you would expect them to be sharpness wise.

After several attempts with MF it appears that the lens does not actually reach an infinity focus, I wound the lens right out at the infinity end as far as it would go and the image was still noticeably soft. By bringing the focus ring down it just became more and more blurred, and I could never find a position for it to focus at infinity (BTW, these trees were about 100-120metres away on 20mm focal length)

So my question is who should I look to send the lens for a good value overhaul and recalibration, as I find myself loving his lens in spite of these shortcomings, and if I could get them fixed I suspect I would love it that much more, being able to shoot fast moving subjects with some confidence??

Sorry for the long post, but if I just asked the last question, doubtless people would have starting asking why, and rightly suggest things I could try, so i'd rather get it said that I've tried it all and I genuinely think it needs attention.

Thanks people for any suggestions
 
its out of warranty (unless its a 3 yr warranty) and sigma will charge for this.
If i understand you correctly you are trying to focus on trees over 100m away @20mm focal length. the trees must be tiny in the frame.

firstly you have to take into account the enviroment and that even air can cause images to look soft. i would ask sigma how they calibrate the lens. i did this with my old 70-200 and they politley told me @200mm you need the test subject to be 8m away with the lens wide open, cant remeber what they said for the 70mm. Any way my point is that you might actually be hoping for more than might be possible with the AF under those conditions and all the varialbles that go with it.

any chance of a pic to help some more.
 
Thank you (of sorts) for your replies. I would not consider the AF a problem without proper reeasoning. Above I have outlined the tests I've done are because of multiple images that haven't focussed with the phase-detect AF, and I'm talking over 100 perhaps, but I've used live view to compensate. Surely that cannot be right? I am not after advice using this lens, or analysis of my tests, as I specifically stated. I want a reasonably priced and well reputed business to service the lens and possibly recalibrate. Something is not right and I missed the warranty dates by blaming myself for the improperly focussed images.

I also don't see how expecting some trees at 100m distance on f/9 to be in focus is asking too much.
 
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How about giving it a go at a closer distance - say 25 metres?
 
if you do need to send it to sigma all the details are here:

http://www.sigma-imaging-uk.com/support/index.htm

my 70-200 is with them at the moment for a service (after 5 years i just felt it was time) and turnaround is 2-3 weeks. the service tarriffs are on the site but if you send it to them theyll do you an estimate before they do any work. but id recommend contacting them before sending to get more info.
 
RichardtheSane - as mentioned above, twice now I think, I am not after an evaluation of my tests, I know there is a problem with the AF, but persevered on advice from another forum that I was at fault not the lens. The lens will consistently fail to focus properly on all manner of scenes and lighting, where as if I use live view it will get it bang on.

Neil_G thanks for the info I was after, a bit disheartening it took till your post to be honest, I could jump through however many hoops people suggest on here to test the lens, but the bottom line is I know there is something wrong and I want it sorted. I'm not looking to prove the fault, but to remedy it.
 
it might be worth, as i think someone else suggested, contacting sigma and asking them if it sounds like a fault or mis-calibration and/or if there is any way to check if the lens is okay though..
 
mumrar said:
RichardtheSane - as mentioned above, twice now I think, I am not after an evaluation of my tests, I know there is a problem with the AF, but persevered on advice from another forum that I was at fault not the lens. The lens will consistently fail to focus properly on all manner of scenes and lighting, where as if I use live view it will get it bang on.

Neil_G thanks for the info I was after, a bit disheartening it took till your post to be honest, I could jump through however many hoops people suggest on here to test the lens, but the bottom line is I know there is something wrong and I want it sorted. I'm not looking to prove the fault, but to remedy it.
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Well you could of just googled "Sigma support" if you felt the answer took to long in coming :naughty: :lol:
 
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mumrar said:
RichardtheSane - as mentioned above, twice now I think, I am not after an evaluation of my tests, I know there is a problem with the AF, but persevered on advice from another forum that I was at fault not the lens. The lens will consistently fail to focus properly on all manner of scenes and lighting, where as if I use live view it will get it bang on.
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This is an forum, you are going to get people trying to help with your primary problem - how were we to know you have taken advice on the problem from another forum?
 
I'm not trying to sound ungrateful, and I know that a lot of great advice can be found on this forum, its one of the reasons I joined. It's just that I did lay out that after so long, and so many varied shots where the phase detect AF misses but the contrast AF doesn't, I knew it wasn't me at fault and I wanted advice on where to go incase there were any good third party companies who could look at it.

Don't be put off by me if I sounded aggressive, I'm trying to be economical on the words due to typing it all out on my phone.

Thanks
 
removed as a fair response made!
 
No worries Matt - thanks. :thumbs:


FYI I have always found Sigma UK to be very helpful - always reply to emails quickly and good to deal with by phone. Hope you get your repair sorted.
 
RichardtheSane said:
FYI I have always found Sigma UK to be very helpful - always reply to emails quickly and good to deal with by phone. Hope you get your repair sorted.
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indeedyho, on the couple of occasions ive dealt with them theyve always gone above and beyond.. i created a couple of threads at the time detailing my delight if youre bored and want to search lol
 
mumrar said:
RichardtheSane - as mentioned above, twice now I think, I am not after an evaluation of my tests, I know there is a problem with the AF, but persevered on advice from another forum that I was at fault not the lens. The lens will consistently fail to focus properly on all manner of scenes and lighting, where as if I use live view it will get it bang on.

Neil_G thanks for the info I was after, a bit disheartening it took till your post to be honest, I could jump through however many hoops people suggest on here to test the lens, but the bottom line is I know there is something wrong and I want it sorted. I'm not looking to prove the fault, but to remedy it.
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I remember a post you made not so long ago with examples in it and it was plainly obvious the lens was at fault and I swear I was the only one seeing it - everyone else was suggesting user error! Get that thing fixed, and maybe while they're at it, they'll fix the CA ;)
 
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