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04-26-2010, 08:29 AM   #1
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Sigma 17-70mm....a bad copy?

Ok...a month or so ago I bought a used Sigma 17-70. After much research I figured this was exactly what I wanted. I liked the focal range, the open front end glass, the 2.8 wide open, etc etc. The price was right too.

I have been playing around with it casually for maybe 6 weeks and I am questioning whether or not it is a bad copy, as has been known to occur with this lens. 50% of my photos are coming out blurry and not sharp at all. I did not have any issues like this with my kit lens. As I am the "indian", "shooting the arrows"....the only consistent part of the equation is me. I am doing nothing different with this lens than I was before with the kit.

So, are they any tests that I can run to see if it really is the lens or if it is operator error? Is the AF function on the Sigma acting differently than the one in the kit lens? therefore affecting the outcome?

Any thoughts would be great. I have VERY little disposable income so if this is a bad copy...I am really screwed.

thanks all.

04-26-2010, 08:51 AM   #2
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Half of it is fuzzy or the entire image? I had to return two to the factory for repair of it (first time they simply gave me a new one).
It's hard to find because it only happens at specific focal lengths/distances...
04-26-2010, 08:56 AM   #3
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good point of clarification.

It is not the entire image....maybe half...if that.

Example, daughter's birthday party yesterday. 5 or 6 kids sitting around while opening presents....most of their faces in focus, except the one all the way on the left side. Now that I think of it...seems like a left side thing predominately...but not always.

If I am not the original owner will Sigma still fix it or replace it?
04-26-2010, 09:00 AM   #4
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I had pretty much the same experience with the Sigma 17-70 lens and finally gave up on it.

Based upon the review database, we seem to be the exceptions though.

Regards,
-tom

04-26-2010, 09:23 AM   #5
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I'd post some comparison photos - same scene, same exposure, same selected focus point (or using manual focus). Without that, it's really hard to say. For instance, it's certainly *possible* you're simply seeing the shallower DOF that comes from wider apertures and longer focal lengths. That would seem totally consistent with the particular situation you described.
04-26-2010, 12:30 PM   #6
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QuoteOriginally posted by Seafood Quote
Example, daughter's birthday party yesterday. 5 or 6 kids sitting around while opening presents....most of their faces in focus, except the one all the way on the left side. Now that I think of it...seems like a left side thing predominately...but not always.
Post pictures of it. I can recognize it by now
Just want to make sure you're not hitting DOF issues.
You're basically looking for a photo where something on the left and right are equidistant from you and if one side is ultra fuzzy at that point, you have something called a "decentering issue". I had to send my lens back twice and my third copy is in good shape...
What was annoying was I couldn't see this all the time. I had to go on vacations where I shot a lot more before I'd notice it. Then send example photos on a CD to Sigma as proof.

No idea if their warranties are to the original owner or not, but I had to send the original receipt as proof of purchase...
04-26-2010, 12:55 PM   #7
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Ok...sounds good. I will try to post some shots.

I am leaving for a week long trip to Joshua Tree NP and my biggest fear is and entire collection of shots completely wasted.
04-26-2010, 01:22 PM   #8
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What aperture are the photos of your kids taken at? If you're taking them at angles at f/2.8 then that's your problem. Your lens might also have front focusing issues though as lots of Sigmas have had those, in which case I think that you can send it back to them and they'll fix that. You can print out a focus test sheet and see if that is what the problem is with your lens.

04-26-2010, 02:23 PM   #9
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For the record, whatever the settings, I have never experienced what you describe. Sorry for you. Post pictures and we'll confirm the issue.
04-26-2010, 03:07 PM   #10
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QuoteOriginally posted by bdery Quote
For the record, whatever the settings, I have never experienced what you describe. Sorry for you. Post pictures and we'll confirm the issue.
+1 to this.. pictures make it much more clear to see what's going on...
04-30-2010, 08:35 AM   #11
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Ok...I know these pictures composition is aweful but they show some of what I am concerned about.

Photo 1 - Look at the girl in the lower left. She is the only part of this picture that is out of focus.


Photo 2 - Again lower left...the lower text on the logo...again...not in focus.

Any thoughts?



04-30-2010, 12:15 PM   #12
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Here is one more. I wear glasses 90% of the time and find manual focusing with glasses a pain and incosistent. So I rely on AF. I took three pictures of this....all three came out eith the text on the sign blurry.

Really getting frustrated.

04-30-2010, 01:14 PM   #13
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First two look ok to me. Looks like it locked on the the background (the stove is in focus in the first photo). In the second photo, it looks like it focuses halfway up the card, but you're in macro mode because you're so close, so the entire thing won't be in focus unless you set it to f/8 or higher. The images are too small to see much else.
The last photo looks like is locked on the fence behind the sight on the right.
Download a copy of PhotoME and confirm your focus points are what's in focus...
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