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Old May 12, 2006, 9:40 AM   #41
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peripatetic wrote:
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I'm with NHL.

My general inclination is to believe the problem is behind the camera not in front.


I don't doubt that inexperienced photographers cause their own problems, but in this case it is hard for me to believe that the explanation is that simple.

If it weresimply user error, would we not expect to see similar issues with Canon's version of the super wide zoom?

It is easy to find comments that the canon lens is "a little soft at 10mm", but almost impossible to find reports that are as serious as the common reports on the Sigma.



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Old May 12, 2006, 11:15 AM   #42
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I would comment here that this is not just that 'fisheye' may not be experienced enough to know how to take a SIMPLE picture. I am sure he can find someone with 'enough experience' to take a picturefor him. :roll:

Maybe we can conclude that any picture taken with Sigma 10-20 and posted on the internet is probably taken by unexperienced user. Well, I wouldn't think so. This lens, as any other wide lens, is most forgiving lens to use.It happened to me to make one soft picture but only at 1/5 sechand-held (night shot). But even that onewas completely soft ... not just one half ... and I still had to zoom in to see it!

I dare anybody here having wide angle lens to make similar to fisheye's street picture ... on purpose ... at 1/125, f/8 ... half-sharp ... half-soft ...

Contest open! :|


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Old May 12, 2006, 2:48 PM   #43
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If you want to test the lens then do it properly.

Print a chart, get the light right, put it on a tripod, etc, etc.

There are plenty of instructions on the net as to how to do this. What you have are suspicions and if you are willing to do the job properly it's really very easy to prove one way or the other.

My point is that 99/100 claims of problems with the lens are not backed up with proof, just vague misgivings because the (inexperienced) user isn't happy with his/her pictures. And such pictures when posted are not of the type that can prove anything conclusively.

It's easy enough to prove when you have a bad lens - set up the charts and do the job properly. Unless you do that your claims will always be suspect.


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Old May 13, 2006, 12:40 AM   #44
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Even though it is possible that unexperiencedphotographer can make shaky picture from what I see I still do not believe that to be the case.

I my rather long years of taking pictures there is no a single one that looks like samples presented. I still wonder how can you make one lake that?

In only one occasion, as I mentioned before, I had to exchange my first digital camera which was Canon A80. I did it after a month of use and I didn't notice the problem right away.

I am an amateur but far from beginner so I can test lens without any charts. I test my lens first with real life pictures and then if I have any suspicion I can go further and take pictures of the charts. Here is comparison between the bad lens (camera)and the good one:

http://community.webshots.com/photo/...37737692cFzGNz


On the left side is my original A80 and on the right side is replacement. Both pictures were taken from the same distance and with the same data. I think that the difference is clear. So if you had a problem with your equipment you will be ready to believe that possibility of faulty equipmentis there.





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Old May 13, 2006, 2:20 AM   #45
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Quote:
I test my lens first with real life pictures and then if I have any suspicion I can go further and take pictures of the charts.
Very sensible.

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I am an amateur but far from beginner so I can test lens without any charts.
LOL - well good for you.

But the point is that if you test them properly - you can say EXACTLY and specifically what is wrong, something a little more detailed than "it's blurry on the right".

I think this horse is dead, I shall cease flogging.
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Old May 13, 2006, 1:46 PM   #46
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Okay friends, here are some intermediary results from today's hardcore testing (took me half a day...)

I did as follows:

used a tripod

mounted my Canon 18-55 kit lens (it's hard to find a more simple and cheaper peace of glass)

focused on the object (a wall), 18mm, Av 8.0, Tv 1/500, ISO 100, shot with timer

did the same with the Sigma 10-20

The wall had lights mounted to the right and to the left side so I compared two pairs of opposit but equivalently positioned lights. The sun was shining from my back.

What I see: the Canon 18-55 is also soft on the right side but softness is so small it's hardly noticable. In comparison, the Sigma 10-20 is very soft on the right side.

There are two possiblities: either the sensor is misaligned and the Sigma shows this effect much stronger or the Sigma (which is already my 2nd copy afterhaving the first one brought back) is faulty.

I keep you informed about the latest developments!

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Old May 13, 2006, 1:49 PM   #47
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Here's the original Sigma 10-20 picture.


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Old May 13, 2006, 3:08 PM   #48
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Quote:
you can say EXACTLY and specifically what is wrong, something a little more detailed than "it's blurry on the right".
Ok, if you take a picture of the chart and picture of the chart is half blury, can you tell me what is specifically wrong?

If picture is blurry, it will be blurry regardless of the subject. Chart is good if you comparing two different lenses. Than you can see which lens has more CA, beter resolution, what kind of distortion. So, in this case, taking picture of the chart will not tell you anything new!

We do not need to agree on everything, that is the reason they named those places as 'discussion forums'. I am maybe more interested in the topic because I have the same lens as fisheye so 'if the horse is dead for you' it is not for me. I will be happy if I was able to help at least a bit!

Now after Fisheye exchanged his lens and new lens shows same kind of distortion (again much more than kit lens) I do not know what to say. There was only one report that I could find on theinternet that somebody exchanged three Sigmas before he got the right one.

I was thinking that maybe lens mount or sensor are missaligned but that would show on thekit lens to. Again, I do not see any reason why 10-20 lens would be more prone to softness (or missalignement) than kit lens? Last test were even made at f8 which is quite small f-stop.

There are couple more things to do:

-find another DSLR body and do more tests

-check your exchange lens serial number

-do test with camera upside-down (will not help if lens mount or sensor are not alligned)

-ask for another exchange or return Sigma and try Canon 10-22; I wouldn't use this lens (or body?) with this 'quality'

How long do you have your camera?
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Old May 13, 2006, 3:12 PM   #49
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Here is another sample with Sigma 10-20 and 'upside-down' test:
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Old May 13, 2006, 3:19 PM   #50
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Right side 1:1 detail; one is 'normal' shot, other camera is 'upside-dwon'.

There is no noticeable difference. Both pictures taken with flash 1/60; f5 from hand. Little difference is maybe because I didn't use tripod, but the point is: difference is negligible.


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