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Old May 10, 2006, 6:47 PM   #21
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Old May 10, 2006, 6:47 PM   #22
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Another one; bad as bad as it could be:


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Old May 10, 2006, 6:48 PM   #23
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Old May 10, 2006, 6:52 PM   #24
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Again, this is not something that would stop me from buying what I think generally is good lens for the money (as this Sigma is - I didn't go for Canon 10-22). I always check internet (that is why we are here on this forum as well) and see if there are potential issues. I do not want to buy lens when it is 'fresh' from bakery. I would rather wait couple of months to see some reports and tests and knowing what potential problem are there makes me a better buyer. :G


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Old May 10, 2006, 10:28 PM   #25
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Thanks everybody for the support!

Although there's a slight possibility that I did something wrong when I took my pictures I really wonder whyall reported cases of faulty lensesconcern problems on the right side of the pictures but nevertalk aboutproblems on the left side or the upper/lower side. This matches my own experience which is shown in the above samples.

Thus,I suspect something's could really bewrong with a couple of copies. I've just got my lense back from the dealer. He's tested it on short focus distances andhe says it's working fine.

I will checkthe lens thorougly onSaturday, particularly on long distance focus whereI see the problems.I willpost the result.

regards,

fisheye
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Old May 11, 2006, 6:57 AM   #26
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Fisheye wrote:
Quote:
I will checkthe lens thorougly onSaturday, particularly on long distance focus whereI see the problems.I willpost the result.
... and that's my beef with your sample image!!!
-> You're only using 1/2 the DOF of the lens on landscape (i.e. the front part only!) when you focus on the far object :idea:

Now if you focus on something closer (and learn about hyperfocal), both the close and far field will be in focus (i.e. you'll be using both front and back parts of the DOF), thus maximizing the distances differences between the sides of an OBTUSE triangle and its base (or when the focal plane is not flat)... IMO you'll see a big improvement (even on a 'bad' lens)

FYI - http://www.vividlight.com/articles/2314.htm
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Old May 11, 2006, 8:43 AM   #27
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I still haven't seen anything that convinces me the lens is bad. ;-)

Did you do as I suggested to begin with?

Quote:
To check to make sure you don't have a lens problem (or misaligned sensor), use a tripod and shoot some newspaper, making sure the camera is absolutely square to it, using the Center Focus point. I wouldn't be surprised if you were using a different focus point for those photos.

Then, check to make sure the print in all 4 cornersis equally soft. Note that it is normal to see some edge softness with most lenses, especially a lens as wide as this one, and especially at wide open apertures. But, all 4 corners should be equally soft using the center focus point when you're square toa flat target like a newspaper. If not, you've got probably got a lens issue or sensor alignment problem (and if the corners are not equally soft, try a different lens to narrow it down to the camera or lens).


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Old May 11, 2006, 10:40 AM   #28
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This is not a new issue with WA lenses especially super wide:
http://photo.net/bboard/q-and-a-fetc...02cXb&tag=

Even the best lenses in the world can not be designed to correct for everything!
-> I kind of drew this up quickly to show what the issue is for this type of lens:
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Old May 11, 2006, 10:42 AM   #29
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NHL, JimC,

I will try your very valuable suggestions on weekend and I'll report the results!

regards,

fisheye
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Old May 11, 2006, 12:12 PM   #30
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I think we are mystifying things a bit. I've made already so many shots with Sigma 10-20 and NONE of the pictures shows THIS MUCH unsharpness. It looks like many people here would just accept this as OK and find every other explanation but not the obvious. I've made close-ups and every angle and distance possible and there is no picture this BLURY!

I would suggest again, go to the dealer and take shots from couple of the same lenses and compare. If you do not have trust in your hands, take a tripod. Lens can be no more than 10% unsharp comparing to the center. What you have is like 60%. Using % is not proper 'method' to compare the quality - it is just an approximation.

And again, try taking same picture with your camera upside-down. This is the best and quickest test! Problem with your lens is not softness but uneven softness and that can be explained in only one way: BAD.

I wouldn't let the dealer take a tests for me! I would respect his opinion but it is you paying $500 and you should be happy with what you have. No dealer should make you a trouble in returing or exchanging the lens.
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