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FORUMS Canon Cameras, Lenses & Accessories Canon EF and EF-S Lenses
Thread started 05 Feb 2007 (Monday) 20:50
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Replacing Canon 17-85 with Sigma 17-70, but is it misfocusing?

 
pythagpython
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Feb 05, 2007 20:50 |  #1

Hey guys,

I decided to get a Sigma 17-70mm to replace my Canon 17-85. It turns out that it isn't so much of a party as it should be. A little background:

I have had the Canon 17-85 for a little over a month now and want to get rid of it because of horrific distortion, CA and OK picture quality. This is especially since most of my photos are taken at 17mm.

So I got the Sigma 17-70 today and was really excited, but when I tested it out, it has been giving me some stress. Pictures taken at 70mm look really bad, as if they are out of focus. It looks like there is some "shadowing". Is there something wrong with it? Please help me out.

Here are some examples:

Sigma @70/4.5

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Canon @ 70/5.6

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Canon Digital Rebel XT | Canon 70-200 f/4 L | Canon 50 1.8 | Tamron 17-50/2.8 | Sold (Canon 17-85 IS, Canon 28-135 IS)

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pythagpython
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Feb 05, 2007 20:54 |  #2

Here is another (worse) case of this:

Sigma @70/4.5

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Canon @ 70/5.6
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Canon Digital Rebel XT | Canon 70-200 f/4 L | Canon 50 1.8 | Tamron 17-50/2.8 | Sold (Canon 17-85 IS, Canon 28-135 IS)

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pythagpython
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Feb 05, 2007 21:25 |  #3

Bump, any suggestions?


Canon Digital Rebel XT | Canon 70-200 f/4 L | Canon 50 1.8 | Tamron 17-50/2.8 | Sold (Canon 17-85 IS, Canon 28-135 IS)

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lungdoc
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Feb 05, 2007 21:37 |  #4

Exif data? Presume tripod used? If slow shutter speed it could be the IS helping the Canon look better. You Might want to try a focus test that's more precise/standardized such as described here http://focustestchart.​com/chart.htmlexternal link
Some also use three AA batteries lined up 3/4'' apart focusing on the middle one.

I guess in the end if it really is off you need to return it if new or repair it if used.

Good luck.


Mark
My Smugmugexternal link Eos 7D, Canon G1X II, Canon 15-85 IS, Canon 17-85 IS, Sigma 100-300 EX IF HSM, Canon 50mm 1.8, Canon 85mm 1.8, Canon 100mm 2.8 Macro, Sigma 50-150 2.8, Sigma 1.4 EX DG , Sigma 24-70 F2.8 DG Macro, Canon EF-S 10-22, Canon 430EX,

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Rumrunner
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Feb 05, 2007 22:05 |  #5

Are the photos cropped?


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pythagpython
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Feb 05, 2007 22:10 |  #6

The photos are cropped 100%, taken on a tripod with remote.


Canon Digital Rebel XT | Canon 70-200 f/4 L | Canon 50 1.8 | Tamron 17-50/2.8 | Sold (Canon 17-85 IS, Canon 28-135 IS)

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pythagpython
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Feb 05, 2007 22:10 |  #7

Oh, and IS was turned OFF on the tripod for the canon.


Canon Digital Rebel XT | Canon 70-200 f/4 L | Canon 50 1.8 | Tamron 17-50/2.8 | Sold (Canon 17-85 IS, Canon 28-135 IS)

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pythagpython
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Feb 05, 2007 23:21 as a reply to pythagpython's post |  #8

Ok, did the focus chart and it is misfocusing. I think I will have to send it back. What do you guys think? I just wish that I could be loving this lens.

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Canon Digital Rebel XT | Canon 70-200 f/4 L | Canon 50 1.8 | Tamron 17-50/2.8 | Sold (Canon 17-85 IS, Canon 28-135 IS)

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pythagpython
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Feb 05, 2007 23:25 as a reply to pythagpython's post |  #9

This is as opposed to the canon, which apparently focuses fine. Sigh... what awful luck...

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pythagpython
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Feb 05, 2007 23:28 |  #10

Ok, so what do you call this? Back focusing? This really stings Sigma's reputation in my mind. I mean, really, what are the chances that my first Sigma lens will have a defect!? Should I give them another try?

Oh yeah, both were taken on tripods, 100% crop.


Canon Digital Rebel XT | Canon 70-200 f/4 L | Canon 50 1.8 | Tamron 17-50/2.8 | Sold (Canon 17-85 IS, Canon 28-135 IS)

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gcogger
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Feb 06, 2007 02:34 |  #11

I had exactly the same thing with my first copy of this lens. The second one is better (although I don't think it's perfect).


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Annabel ­ Doskey
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Feb 06, 2007 04:49 as a reply to gcogger's post |  #12
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f/4.5 @70mm on this lens is wide open for that extension. Try reshooting the focusing chart at f/5.6 and then f/8.




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Ospi
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Feb 06, 2007 05:53 |  #13

Bah looks like im back focusing big time. Now the question is, where do you send it to get repaired?


Canon EOS 70D
Sigma 150-600mm f/5-6.3 Contemporary

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pythagpython
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Feb 06, 2007 06:40 |  #14

Ospi wrote in post #2663565external link
Bah looks like im back focusing big time. Now the question is, where do you send it to get repaired?

It seems like this is a common problem with this lens. WTF is wrong with Sigma's QC?! :mad: I think I'm going to send it in for a replacement.


Canon Digital Rebel XT | Canon 70-200 f/4 L | Canon 50 1.8 | Tamron 17-50/2.8 | Sold (Canon 17-85 IS, Canon 28-135 IS)

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Ospi
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Feb 06, 2007 06:43 |  #15

pythagpython wrote in post #2663693external link
It seems like this is a common problem with this lens. WTF is wrong with Sigma's QC?! :mad: I think I'm going to send it in for a replacement.

Yeah QC does seem to be a bit of a problem, then again i think they would rather risk not being as precise with their lenses in order to make them cheaper and rollout faster and take the hit with the 5% odd focusing problem.

though when i spend $400 i like to think its going to arrive 100% perfect.


Canon EOS 70D
Sigma 150-600mm f/5-6.3 Contemporary

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Replacing Canon 17-85 with Sigma 17-70, but is it misfocusing?
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