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07-20-2011, 06:37 PM   #1
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Sigma lenses calibrated to a body

I'm curious to know if anybody here has had experience with Sigma calibrating one of their lenses to a specific body because of front/back focusing or other issue. Were the final results to your liking? Did the calibration reveal anything of concern about the body itself?

My story begins with me missing the DA* 16-50mm I sold a while back. I thought I'd do more with prime lenses, and I'm trying my hand at it, but I still missed the versatility of a standard zoom. I bought a Tamron 17-50mm 2.8 that went back almost immediately because it was shockingly unusable with focusing flaws; I can't believe it even left the factory. After that I bought a Sigma 17-50mm 2.8 which also went back. The Sigma, too, had a pretty bad front focusing issue. I exchanged this for a second Sigma which, at first, seemed reliable. But after six weeks a back focusing issue became apparent and the corners were unacceptably soft, even at mid-range apertures.

I sent the lens to Sigma with a description of the problem and within the week they contacted me. However, they told me the lens was doing the opposite of my description, that the lens actually had a front focusing problem. They requested that I send in my Pentax (a K-5) and they would adjust the firmware on the lens accordingly. They told me what I was seeing compared to what their equipment was measuring was probably due to some difference in the beam splitter portion of my DSLR's auto focus mechanism. I will be sending in my camera next week so they can calibrate the lens.

Because I'm a bit of a hypochondriac when it comes to issues with my camera (and especially since this is relatively new - I've only had it for a few months) this makes me concerned there's something wrong with the K-5. However, I'm hoping somebody can talk me out of my hallucinations!

I can't say any of my other lenses exhibit issues that differ from when I used them with my previous body, a K-7. My DA* 50-135mm is working like a champ, my Tamron and Sigma macros seem to be behaving normally, and my current workhorse, an aging Sigma 28-105mm 2.8-4 really shines now that it can be paired with the K-5's great high ISO performance.

So... why would my camera's auto focus system cause the lens to behave in contradiction to Sigma's measurements? I've heard of people having their Sigma lenses re-chipped or having the firmware adjusted because of a new body, but I was under the impression that was because the lens simply didn't recognize the new camera model. And going back to my first paragraph, if any of you have had similar experiences with Sigma and calibration, can you tell me if you/they were successful in solving the problem?

Thank you all kindly in advance for your time and advice!

07-29-2011, 10:10 PM   #2
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So... nobody here has ever had a lens even adjusted by Sigma itself?
07-30-2011, 04:15 AM   #3
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First, those firmware updates are for some flashes

There is nothing wrong with your K-5. Because manufacturing tolerances can never ensure 100% reliability (reasonable targets usually are 2 standard deviations assuming a normal spread of samples, or 95,45%), it can occur that a body and a lens show a mismatch outside acceptable limits. That's why the body can be used to properly correct the lens. It will become "outside tolerances" but will be within your camera's tolerances

Does tgat help?
07-30-2011, 05:41 AM   #4
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First of all, I think it is great service from Sigma that they offer to calibrate the lens with your camera.

If you are happy with how your camera performs with other lenses, you may want to tell them that you don't not wish the camera to be altered/adjusted in any way.

Have you tried the AF adjust feature of the K-5 to counteract the backfocus issues you saw? What approach did you use to determine that the lens is backfocusing?

Maybe you want to consult the AF adjustment hints I compiled.

11-17-2011, 07:19 PM   #5
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LowVoltage: I'm waiting for my camera/lenses to come back from Sigma, so I'm curious how things turned out for you. Did you send you camera to Sigma? Did that take care of the issues you were having with the 17-50mm? Did you camera behave as it did before with your other lenses?
11-18-2011, 02:07 AM   #6
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I have had a Sigma lens calibrated to a body.
Turned out perfect.
Only problem is that the lens on a new body needs a focus correction of -8 now.
11-19-2011, 08:16 AM   #7
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My Sigma EX non-OS lenses (24-70 and 70-200) both needed calibration. I couldn't do it myself using in-body micro-adjustment as it needed beyond -10. So once my busy season began to slow down, I sent my backup body and both Sigma lenses in for calibration.

They don't mess with your camera. They just use it as a reference to calibrate the lenses to. I just made sure to reset my camera AF adjustments to 0.

Lenses were back within two weeks from me shipping them in.

So far so good - marked improvement from before.
11-19-2011, 03:46 PM   #8
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I've never had a Sigma or other lens physically calibrated to a certain camera. I prefer to use the Camera's AF adjustment as I have two K-5s bodies and often the adjustments are different for each body. PLus when I sell teh K-5s to get a couple of K3s next year [ ] I can simply use the AF adjustment again.

from my experience I've had to adjust AF just as much for pentax and sigma lenses. the only lens I have which needs more than +/-10 is my Pentax A 50mm f/1.2. but I always manually focus it anyway and would never rely upon the focus confirmation.

11-19-2011, 04:46 PM   #9
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QuoteOriginally posted by Smeggypants Quote
I've never had a Sigma or other lens physically calibrated to a certain camera. I prefer to use the Camera's AF adjustment as I have two K-5s bodies and often the adjustments are different for each body.
I don't think I would like having two identical bodies with different calibrations. If that was the case, I would think about sending them in to Pentax to have them both calibrated perfectly. But I'm not sure if this is a service that Pentax offers for free, or at all.

I only have one body to worry about, and if my K-x allowed adjustments for individual lenses, I would have just tried that first. The lens adjustment features are one of the reasons I've been tempted to upgrade to the K-5. But for the time being, I'll wait to see what the replacement for the K-r brings. If it has the 16MP sensor and lens adjustment, it'll be a no-brainer.
11-19-2011, 06:09 PM   #10
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Not sure if everyone has seen this:

LensRentals.com - "This lens is soft" and other myths
11-19-2011, 11:24 PM   #11
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QuoteOriginally posted by Edgar_in_Indy Quote
I don't think I would like having two identical bodies with different calibrations. If that was the case, I would think about sending them in to Pentax to have them both calibrated perfectly.
I agree. Interestingly, both my Sigma Lenses needed beyond -10 on both my K5 and K20. Now that Sigma calibrated the lenses to 0 on my camera, if I needed to do micro-adjustments at least it would be within the range offered by the cameras.

Per my work order for both lenses, firmware was updated plus adjustment of AF Data was performed.
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