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08-12-2013, 07:29 AM   #1
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SMC Pentax-DA* 16-50mm F2.8 ED AL [IF] SDM: How to correct for distortions?

I have owned the SMC Pentax-DA* 16-50mm F2.8 ED AL [IF] SDM since December, and all in all I'm happy with it. However, when I do group photos at 16mm (as I do, inevitably, in party situations where I need the widest angle possible), the barrel distortion gets painful. People have very unflattering facial proportions.

How do the rest of you deal with this? I have tried manual corrections in GIMP some times with some luck, but having finally purchased Lightroom I notice that it's possible to apply "custom lens correction profiles". Does something like that exist for this lens?

All advice appreciated, thanks.

08-12-2013, 07:42 AM   #2
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I think the DA*16-50 has a profile in Lightroom. I'm not home to check, but the latest Lightroom should be pretty updated.
08-12-2013, 07:59 AM   #3
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First of all, don't shoot portraits at 16mm unless you can't help it. Second, there is a lens profile in lightroom that corrects itto a certain extent, but it doesn't work miracles.
08-12-2013, 08:03 AM   #4
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The cam can also do on-board corrections, but there's only a drawback in lengthening processing time. Send it to LR and select for the lens correction there. And yes, at 16mm, this lens is not a winner. It's better looked at as a 17-18 on the wide end, not only due to distortion. It's just optically not very good in that range.

08-12-2013, 08:03 AM   #5
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08-12-2013, 08:38 AM   #6
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QuoteOriginally posted by MetteHHH Quote
having finally purchased Lightroom I notice that it's possible to apply "custom lens correction profiles". Does something like that exist for this lens?
Yes! just scroll down on your right until you reach "Lens corrections" and check the "Enable lens corrections" box. If your lens isn´t recognized automatically (happens to me with the DA16-50 for some reason), you can select manufacturer and model manually.
Then go to "Color" tab (you where on "Profile" tab) and check the "Remove chromatic aberrations".... Bualá! jaja
08-12-2013, 08:42 AM   #7
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QuoteOriginally posted by carrrlangas Quote
Yes! just scroll down on your right until you reach "Lens corrections" and check the "Enable lens corrections" box. If your lens isn´t recognized automatically (happens to me with the DA16-50 for some reason), you can select manufacturer and model manually.
Then go to "Color" tab (you where on "Profile" tab) and check the "Remove chromatic aberrations".... Bualá! jaja
Select "default", then it will recognize it, provided it's in the database.
08-12-2013, 08:56 AM   #8
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QuoteOriginally posted by snake Quote
Select "default", then it will recognize it, provided it's in the database.
It was on "Default". It auto-completes once i choose the "Make" but you gave me the idea to click "Save new lens profile Default" after the lens info was completed. So now it works automatically! Thanks a lot!

08-12-2013, 09:39 AM   #9
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The lightroom profile should get rid of barrel distortion but the natural wide-angle distortion at the frame edges is unavoidable as far as I'm aware. Try making sure no one stands near the frame edge when taking the shot, or zoom in and stand back.
08-12-2013, 10:48 AM   #10
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I suspect the problem you would (and should) most notice, at 16 mm, is perspective distortion, not barrel distortion. If you have to go that wide, I'm not sure there is any way to get a flattering picture of someone's face when their nose is that much closer to the camera. Maybe there is a way to post process this, but this would be adding distortion to achieve the desired effect, rather than correcting a fault of the lens.
08-13-2013, 02:09 AM   #11
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Thanks for all the helpful comments. I would never take portraits at wide angle, but particularly when using this indoors for party scenes it is rather unavoidable that there will be faces near the edges. I can see the logic of this being perspective distortion - I suppose the reason I never considered the problem before is that I have never been much of a wide-angle shooter.

I will definitely try out the Lightroom correction and see how much that alleviates the problems. Thanks for the walk through - I got Lightroom for my birthday but I have spent the bit of time I have had processing photos since with the actual photos, rather than watching tutorials.

I'm no fan of video tutorials anyway, I am so sorry they are taking over from the written ones. I like reading. I hate watching other people do stuff, rather than just learning the procedures on my own. But that is a different topic really. Thanks a lot for all the tips and good points!
08-13-2013, 03:58 AM   #12
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I too recently noticed lots of distortion at 16mm of the DA* 16-50 when taking a picture of a large group. LR profile didn't help much. Wondering if DA 16-45 has less distortion at the wide end. Have to check that, at least I don't remember distortion being as pronounced as with the DA*.
08-13-2013, 04:06 AM   #13
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IMO, Sigma and Tamron's f2.8 zooms are more usable at 17/18 than the Pentax is at 16. If you want less distortion, then it's Full Frame and the appropriate lenses and switching styles/distances a bit.
08-13-2013, 09:21 AM   #14
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QuoteOriginally posted by snake Quote
IMO, Sigma and Tamron's f2.8 zooms are more usable at 17/18 than the Pentax is at 16. If you want less distortion, then it's Full Frame and the appropriate lenses and switching styles/distances a bit.
Never had an issue using my 16-50 at 16, and surely switching to full frame and a 24-70 or whatever would land you in the same ball park?

It is difficult when you're in a small room and need a very wide group shot. Perhaps try and casually put the less body-image conscious towards the frame edge? Never tried fixing perspective distortion of this sort, let me know how it turns out.
08-13-2013, 02:57 PM   #15
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I don't see how a FF would reduce distortion. I mean, tiny little sensors in P&S cameras are perfectly capable of taking undistorted portraits, right?

I keep telling my relatives to stop taking those cheesy self-portraits with their cell phones. It's not the cell phone, rather it's the 2-1/2 foot distance between the lens and their nose that makes them look so odd.
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