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

pythagpython · 5th of February 2007 (Mon)

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

s45.jpg

Canon @ 70/5.6

c56.jpg

pythagpython · 5th of February 2007 (Mon)

Here is another (worse) case of this:

Sigma @70/4.5
s245.jpg

Canon @ 70/5.6
cv56.jpg

pythagpython · 5th of February 2007 (Mon)

Bump, any suggestions?

lungdoc · 5th of February 2007 (Mon)

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.html
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.

Rumrunner · 5th of February 2007 (Mon)

Are the photos cropped?

pythagpython · 5th of February 2007 (Mon)

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

pythagpython · 5th of February 2007 (Mon)

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

pythagpython · 5th of February 2007 (Mon)

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.

pythagpython · 5th of February 2007 (Mon)

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

pythagpython · 5th of February 2007 (Mon)

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.

gcogger · 6th of February 2007 (Tue)

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).

Annabel Doskey · 6th of February 2007 (Tue)

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.

Ospi · 6th of February 2007 (Tue)

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

pythagpython · 6th of February 2007 (Tue)

Quote:

Originally Posted by Ospi

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?!

I think I'm going to send it in for a replacement.

Ospi · 6th of February 2007 (Tue)

Quote:

Originally Posted by pythagpython

It seems like this is a common problem with this lens. WTF is wrong with Sigma's QC?!

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.

5th of February 2007 (Mon)	#1
pythagpython Member Join Date: Dec 2006 Location: New York City, NY Posts: 148 IMAGE EDITING OK	Replacing Canon 17-85 with Sigma 17-70, but is it misfocusing? 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 s45.jpg Canon @ 70/5.6 c56.jpg __________________ 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)

5th of February 2007 (Mon)	#2
pythagpython Member Join Date: Dec 2006 Location: New York City, NY Posts: 148 IMAGE EDITING OK	Re: Replacing Canon 17-85 with Sigma 17-70, but is it misfocusing? Here is another (worse) case of this: Sigma @70/4.5 s245.jpg Canon @ 70/5.6 cv56.jpg __________________ 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)

5th of February 2007 (Mon)	#3
pythagpython Member Join Date: Dec 2006 Location: New York City, NY Posts: 148 IMAGE EDITING OK	Re: Replacing Canon 17-85 with Sigma 17-70, but is it misfocusing? 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)

5th of February 2007 (Mon)	#4
lungdoc Goldmember Join Date: May 2006 Location: St. Catharines, Ontario Canada Posts: 2,051 IMAGE EDITING OK	Re: Replacing Canon 17-85 with Sigma 17-70, but is it misfocusing? 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.html 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 Smugmug Eos 7D, 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,

5th of February 2007 (Mon)	#5
Rumrunner Senior Member Join Date: Jun 2006 Location: El Paso, Texas Posts: 1,865 IMAGE EDITING OK	Re: Replacing Canon 17-85 with Sigma 17-70, but is it misfocusing? Are the photos cropped? __________________ Gear List

6th of February 2007 (Tue)	#11
gcogger Goldmember Join Date: Mar 2003 Location: Southampton, UK Posts: 2,538 IMAGE EDITING OK	Re: Replacing Canon 17-85 with Sigma 17-70, but is it misfocusing? 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).

6th of February 2007 (Tue)	#12
Annabel Doskey User is banned from forums Join Date: Jan 2007 Posts: 41	Re: Replacing Canon 17-85 with Sigma 17-70, but is it misfocusing? 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.

6th of February 2007 (Tue)	#13
Ospi Senior Member Join Date: Jun 2005 Location: Brisbane, Australia Posts: 1,014 IMAGE EDITING OK	Re: Replacing Canon 17-85 with Sigma 17-70, but is it misfocusing? Bah looks like im back focusing big time. Now the question is, where do you send it to get repaired? __________________ Canon EOS 40D Canon 10-22mm f/3.5-4.5 \| \| Canon 70-200 f/4L IS \| Sigma 17-70mm f/2.8-4.5 DC \| Sigma 50mm f/1.4 DG HSM \| Canon 580EX II Full Gear \| Gallery Last edited by Ospi : 6th of February 2007 (Tue) at 06:11.

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