Go Back   Steve's Digicams Forums > Digital SLR and Interchangeable Lens Cameras > Canon Lenses

Reply
 
Thread Tools Search this Thread
Old May 9, 2006, 8:05 PM   #11
Senior Member
 
Join Date: Mar 2006
Posts: 171
Default

I have Sigma 10-20. I think you have 'one of those' that has to be returned. There were number of complaints about this lens and usually about softness (extreme-and that is what you have) on the right side. I am sorry to say, but your sample is terribly bad.

The best way to test your lens is take two pictures of the same subject: one picture take in normal way and other one turn your camera upside-down. This way you will see if your optics is 'symetrical'; if you have a bad sample, your picture is going to be unsharp at the left side.

This lens can get a bit unsharp at the extreme corners and that may depends on how the picture was taken. Softness can be seen only at 1:1 and not with reduced size as is your sample. From what I see you have it to much and you need to return it. If you bought it localy it is an easy thing to do. Just go and try another one and compare. Take your lens serial number (just in case)!

About CA, again, it can happen with this lens again at the corners and at the edges with lots of contrast. There is nothing you can do about it. There is a software (for free and I do not remember the name) that can substantially remove. I do not find it to annoying. With this kind of lens there is always some unsarpness at the corners.

Alos, look at my post about this lens and couple of sample pictures.

I understand your dissapointment, but once you get the good one you will be happy with it!

GM2006 is offline   Reply With Quote
Old May 9, 2006, 10:14 PM   #12
Senior Member
 
Join Date: Mar 2006
Posts: 171
Default

Here is the sample from what I believe is a good sample of Sigma 10-20:

(1/125; f8; 10mm; -2/3 exp comp)



Attached Images
 
GM2006 is offline   Reply With Quote
Old May 9, 2006, 10:15 PM   #13
Senior Member
 
Join Date: Mar 2006
Posts: 171
Default

Upper left corner (minimal CA and softness):


Attached Images
 
GM2006 is offline   Reply With Quote
Old May 9, 2006, 10:16 PM   #14
Senior Member
 
Join Date: Mar 2006
Posts: 171
Default

And right-upper corner; a bit softer and bit more CA but I would say, normal for this kind of lens:
Attached Images
 
GM2006 is offline   Reply With Quote
Old May 9, 2006, 10:17 PM   #15
Senior Member
 
Join Date: Mar 2006
Posts: 171
Default

And center crop:
Attached Images
 
GM2006 is offline   Reply With Quote
Old May 10, 2006, 3:19 AM   #16
Super Moderator
 
peripatetic's Avatar
 
Join Date: Nov 2004
Posts: 3,599
Default

I'm with NHL.

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

With your new lens go to the same spot and take the same shot. Then do as he suggests and stand in the middle of the road, etc.

Look up how to shoot test charts under controlled conditions too if you really want to test your lens.

Are there really no "bad copies" out there?

No surely not - but those very few bad copies have spawned a rash of novices blaming their equipment when their technique is at fault. In 99% of cases the sample shots that are posted do not show conclusively that there is a problem with the lens, but are fairly good indicators of lack of understanding.

Sometimes this person will go back 3 or 4 times to the shop until they finally (through luck) take some shots they are happy with and proudly declare they have found a "good copy".

Strangely I have NEVER, not even once, seen a photography magazine come back with the claim that they got a bad copy for testing.

I just don't buy it.
peripatetic is offline   Reply With Quote
Old May 10, 2006, 11:54 AM   #17
Senior Member
 
Join Date: Mar 2006
Posts: 171
Default

Quote:
Strangely I have NEVER, not even once, seen a photography magazine come back with the claim that they got a bad copy for testing.
I wouldn't always take for granted what photo-magazines say. Even if I try my hardest I couldn't make my picture be so much unsharp at only one half. Unless you are realy a total beginner (and I believe most of us are not) it is not that difficult to judge the quality of the lens.

Before I bought this Sigma 10-20 I've checked internet to see what other people have to say. If you take your picture with tripod and small f-stop and your picture is still unsharp then your lens is just bad. Again I do not have to believe what 'other people' have to say but I do not have to ignore it either.

Thanks to digital technology you do not need to do big enlargments anymore to be able to check how good your optics perform.

I am always ready to believe that there is faulty equipment. My first digital camera was Canon A80, at the time one of the best point-and-shoot available. I didn't have other camera to compare with but I've noticed unacceptable softness at f 2.8. I've taken number of test shots and same problem repeated over and over. You do not need to be an expert to see that picture is not sharp. All the reviews of this particular camera were excellent and nobody ever complained. But I've returned it and exchanged it for another and took the same shots again. The difference was at least 50% in improved sharpness. This is just one example that even manufacturer with a good reputation, as Canon is, can have bad quality testing. There are so many things that can go wrong with such a complex device that I can understand that sometimes quality check fails. I am not even sure that they would test every camera on the factory floor.

When I went to my camera shop I've told them that I will return the lens if I find it soft as 'some people' on internet pointed out. He understood and said that there were cases with any lens manufacturer that optics was not up to standard.

If digital camera is to difficult to be thoroughly tested, I do not understand why is to difficult to test every lens produced. With todays computer equipment and advanced software it wouldnt be that difficult. You do not need to much training to check the lens. In general, there are much more complaints with Sigma lenses than with other manufacturers.



GM2006 is offline   Reply With Quote
Old May 10, 2006, 2:31 PM   #18
Super Moderator
 
peripatetic's Avatar
 
Join Date: Nov 2004
Posts: 3,599
Default

Well, you'll have your new lens soon enough and can post a comparison shot.
peripatetic is offline   Reply With Quote
Old May 10, 2006, 6:46 PM   #19
Senior Member
 
Join Date: Mar 2006
Posts: 171
Default

I hope he will replace his lens asap. Here are some other bad samples from internet. I am not showing them to argue but more as help to others - I think that for couple of hundreds of $ you have to have GOOD lens; bad samples'are there'. I was lucky:


Attached Images
 
GM2006 is offline   Reply With Quote
Old May 10, 2006, 6:46 PM   #20
Senior Member
 
Join Date: Mar 2006
Posts: 171
Default

Right side:
Attached Images
 
GM2006 is offline   Reply With Quote
 
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -5. The time now is 4:23 PM.