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Old Sep 2, 2010, 1:53 PM   #1
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Default Front-focus issues?

Going thru a bunch of pics last night, especially of this friendly little guy (gal?) I noticed in almost all of them the image is off balance as far as what is in focus. Notice how focused the grass in front of him is and how quickly the background is blurred. I know the focus point was right since i was only a few feet away and I also know Sigma has a reputation for producing lenses with front or rear focus issues. I hadn't really given it much thought until last night. After using the tamron so much of late I realized the bokeh is so different, the image is clear in the middle and BOTH front and back not so much, which is what i would expect with larger apertures. What do you all think? Might explain why the Sigma seems softer than it should.

John
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Old Sep 2, 2010, 3:07 PM   #2
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Which Sigma lens did you use in that picture? I have the Sig 55-200mm and have not noticed that problem. But my subjects are usually farther away. Do you think it is more likely to happen when you are using short focusing distances?

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Old Sep 2, 2010, 5:05 PM   #3
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Which Sigma lens did you use in that picture? I have the Sig 55-200mm and have not noticed that problem. But my subjects are usually farther away. Do you think it is more likely to happen when you are using short focusing distances?
Hi Steven, it's the 135-400. Since I really only just started thinking about this issue last night I'm not sure. It shows up more in this series of pics and it could be because of the short distance. Or it could just be because there's something to see if it's front focused. At longer distances it seems like what I'm shooting doesn't have as obvious a foreground so it might just look a little soft. Sharpness wise the lens is only equal to my Tokina at 400mm and may not be even as sharp as the Tamron at 200mm. Seems to me it should be better than that.

John
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Old Sep 2, 2010, 6:42 PM   #4
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But my subjects are usually farther away.
Well you could try shooting less dangerous animals than crocs.

(Sorry, I too like to jerk peoples chains. )

Ted
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Old Sep 2, 2010, 8:39 PM   #5
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Well you could try shooting less dangerous animals than crocs.

...........................Ted
You mean animals like harmless little sleeping kitty cats??

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Old Sep 2, 2010, 9:18 PM   #6
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I LOVE this shot! Just a little house pet, relaxing. C'm here, little kitty...

Ted
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Old Sep 3, 2010, 5:15 AM   #7
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Default sigma 135-400mm lens

Hi John,

I too have the Sigma 135-400mm lens and I did recalibrate the lens as it did exhibit front focusing issues.

The procedure I used can be found here:

http://www.prophotohome.com/lens-cal...it-peter-gregg.

You can buy a lens calibrating gauge, in fact I think Ted has one. But, this procedure is a bit less expensive.

The E-30 has the capability of being able to adjust and store AF adjustments for a particular lens. I don't know if your E-1 has that capability.

I also, did contact Sigma and inquired if they could calibrate a lens. They said they could but would need the lens and camera in order to make the correction.

Zig
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Old Sep 3, 2010, 7:42 AM   #8
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Hi John,

I too have the Sigma 135-400mm lens and I did recalibrate the lens as it did exhibit front focusing issues.

The procedure I used can be found here:

http://www.prophotohome.com/lens-cal...it-peter-gregg.

You can buy a lens calibrating gauge, in fact I think Ted has one. But, this procedure is a bit less expensive.

The E-30 has the capability of being able to adjust and store AF adjustments for a particular lens. I don't know if your E-1 has that capability.

I also, did contact Sigma and inquired if they could calibrate a lens. They said they could but would need the lens and camera in order to make the correction.

Zig
I do have the Lens Align Lite. It works well but is tedious to set up unless you have a helper. You have to get the lens and the Lens Align parallel so you do a lot of moving back and forth between them if you're alone. Also, you really need to have 2 tripods.

Having Sigma calibrate the lens might not be more expensive than the $80 for the Lens Align Lite. But I'd want to be darned sure they didn't monkey with the camera settings, only the lens...

Ted
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Old Sep 3, 2010, 8:05 PM   #9
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Thanks Ted and Zig. I don;t see anything in the menus or manual of the E-1 that talks about focus calibration so maybe that feature wasn't offered at the time. I'll have to see if the focus is the same on the 500, I assume it is. I can live w/o the Sigma much more than I can w/o the E-1 so sending them both in is out of the question. I suppose I could send the 500 and just use it with the sigma.....or I could quit using old bodies

John
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Old Sep 3, 2010, 10:03 PM   #10
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Thanks Ted and Zig. I don;t see anything in the menus or manual of the E-1 that talks about focus calibration so maybe that feature wasn't offered at the time. I'll have to see if the focus is the same on the 500, I assume it is. I can live w/o the Sigma much more than I can w/o the E-1 so sending them both in is out of the question. I suppose I could send the 500 and just use it with the sigma.....or I could quit using old bodies

John
John, I don't think any Oly camera offered specific lens focus calibration prior to the E-30. The E-3 doesn't.

Ted
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