[danielnicholson]

Hello,



Long term reader on this excellent site but this is my first contribution.



I've used the Sigma 10-20mm for several years, and since I bought it I have had an issue whereby the entire left hand side of the frame (approx 400-600 pixels worth on the full size JPG) is very soft. The rest of the frame, including the far right hand side, is absolutely fine and perfectly sharp. I stupidly didn't bother getting it checked by Sigma whilst it was still under warranty, and simply learnt to frame my subjects avoiding anything of importance from being in the far left of the shot. A photographer friend of mine at the time (who was more experienced than me) suggested stopping down as far as possible, preferably between f11 and f14, and that this should help me to keep the images as sharp as possible. Now after several years I am beginning to question his advice.



Now, I have to admit that whilst I take photos day in day out and have had numerous photos published (mainly aviation photography), I know very little when it comes to the technical aspects of photography. It is something that I'm slowly but surely trying to learn! However, am I right in thinking that this lense should have a 'sweet' spot and that by stopping down as far a f14 I may well be making the softness worse? Has anyone else had similar experience with this lense, or have I just managed to get a 'bad copy'?



It's got to the point now where I am seriously considering a new wide angle lenses, but I will only settle for a new lense if there will be a definite improvement in the image quality. To establish this, I need to ensure whether or not I'm getting the best out of what I already have!



Many thanks in advance for your thoughts.

[popo]

If one side of the image is noticeably soft, that was a lens flaw and you should have got it checked out under warranty.



Putting that aside, stopping down generally helps up to the point where diffraction softening takes over, and further stopping down just makes everything softer. But you're trading against depth of field when you do so. You need to decide where that point it. Best way is to try it yourself. Try using f/5.6, f/8, f/11, f/16 on a scene and compare them.

[danielnicholson]

[quote name='popo' timestamp='1334853564' post='17618']

If one side of the image is noticeably soft, that was a lens flaw and you should have got it checked out under warranty.



Putting that aside, stopping down generally helps up to the point where diffraction softening takes over, and further stopping down just makes everything softer. But you're trading against depth of field when you do so. You need to decide where that point it. Best way is to try it yourself. Try using f/5.6, f/8, f/11, f/16 on a scene and compare them.

[/quote]



Thank you popo, I'm assuming that this is a definite flaw in the lense and I should have got it sorted. I have attached an example photo, I have re-sized to 1600px wide so that it meets the file size limit but other than that I have not edited anything. At 17mm and F14 I wouldn't expect the left (particularly the entire top left corner) to be so soft whilst the rest of the image appears fine. Next time the sun is out, I shall try some shots from back garden at different focal lengths and apertures to see whether I can spot any patterns and potentially rule out particularly bad areas from further shots.



Meanwhile, does anyone here have experience of the Sigma 8-16 f4.5-5.6 and the Tokina 11-16 f2.8? I have decided that if I do get a new wide angle lenses then it will probably be one of these two - I can't decide whether I want the crazy wide 8mm to have some fun with or whether I should settle for the faster Tokina which I assume would be much better for indoor photography.

[danielnicholson]

Ok, I thought I'd attached a photo to the post above but I can't see it..this should do it.

[davidmanze]

[quote name='danielnicholson' timestamp='1334842004' post='17601']

Hello,



Long term reader on this excellent site but this is my first contribution.



I've used the Sigma 10-20mm for several years, and since I bought it I have had an issue whereby the entire left hand side of the frame (approx 400-600 pixels worth on the full size JPG) is very soft. The rest of the frame, including the far right hand side, is absolutely fine and perfectly sharp. I stupidly didn't bother getting it checked by Sigma whilst it was still under warranty, and simply learnt to frame my subjects avoiding anything of importance from being in the far left of the shot. A photographer friend of mine at the time (who was more experienced than me) suggested stopping down as far as possible, preferably between f11 and f14, and that this should help me to keep the images as sharp as possible. Now after several years I am beginning to question his advice.



Now, I have to admit that whilst I take photos day in day out and have had numerous photos published (mainly aviation photography), I know very little when it comes to the technical aspects of photography. It is something that I'm slowly but surely trying to learn! However, am I right in thinking that this lense should have a 'sweet' spot and that by stopping down as far a f14 I may well be making the softness worse? Has anyone else had similar experience with this lense, or have I just managed to get a 'bad copy'?



It's got to the point now where I am seriously considering a new wide angle lenses, but I will only settle for a new lense if there will be a definite improvement in the image quality. To establish this, I need to ensure whether or not I'm getting the best out of what I already have!



Many thanks in advance for your thoughts.

[/quote]

Hi,

I had the same problem with this lens at 10mm, there is nothing else to do but return it to Sigma! I had to wait 2 months for a repair as they were short of spares,yes they change the elements/groups.

It was well worth it, as returned, it was better centered not perfect but nearly(it seems that's what we have to expect these days) anyway now it's a very sharp lens.I think it was with the 10-20mm 4/5.6 that photozone stated that they had to test 4 lenses before finding one that was acceptable.

I find at 10mm for sharpness across the frame F11 (to get good corners) although F8 maybe gives a better center,12-20mm is best at F8.

Ring Sigma,they're pretty good, if you explain the situation maybe they will be sympathetic!



Dave's clichés

[Rover]

I had the same problem with my 16-35 L II after dropping it onto the ground. It was decentered and had to go in for servicing.