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10-24-2011, 07:15 PM   #1
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15mm or 21 mm? which is better controlling barrel distortion

i know about lens correction on the k-5, and shooting raw and all that, but which of the da lenses, either the 15 or 21 has the better controlling barrel distortion on it's own? anyone tried both ?

10-24-2011, 07:24 PM   #2
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There is no controlling barrel distortion, it's a property of the lens. Do you mean perspective distortion? In that case the DA21 has less becuase it is a longer lens. As you shoot you can control it by keeping it parrellel to the ground.

I use PTLens on both my DA15 and DA21 (at times, not for every shot) to correct perspective distortion and for the DA21 barrel, however for some reason PTLens doesn't have a DA15 profile to correct barrel, but luckily it has very little anyway.

That clear? I rambled a bit there....

Edit: Oh yeah, there is in camera correction for barrel distortion, but only for jpegs, it doesn't correct RAWs.

This is an example perspective distortion, in camera does nothing for this in jpeg or RAW, notice how the poles and buildings are leaning over....


Last edited by twitch; 10-24-2011 at 07:31 PM.
10-24-2011, 07:38 PM   #3
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not sure what you mean about perspective distortion vs barrel distortion, but which lens took this shot? the lines seem distorted, but not curved, ( which is what i meant by barrel distortion, curving lines ) the shot above is kind of nice even with the tilted angles, less objectionable to me personally than the curving lines. thanks.
10-24-2011, 08:05 PM   #4
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21 seems to have more barrel distortion.

15.


21.


15.


21.


10-24-2011, 08:53 PM   #5
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Perspective distortion is explained pretty well on wikipedia, but the short version is, any time you shoot with a wide angle lens, you are taking a scene wider than a typcal picture frame frame and stuffing it into too small a space, and this causes things to look different than they do in real life. It's unavoidable, and not a lens flaw. The wider the lens, the more perspective distortion, so the 15 has more than the kit lens at 18, which in turn has more than the 21. Barrel distortion and pinchusion distortions are lens flaws, and the 21 has more than most by a pretty large margin, while the 15 is remarkably free of them.
10-25-2011, 06:30 AM   #6
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thanks twitch, special k, and marc.
11-01-2011, 02:09 PM   #7
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According to Photozone, the DA15 has approx. 1.5% barrel distortion and the DA21 approx. 2%. Distortion can easily be dealt with in PP when it has no irregular pattern. As those two lenses have their profile in LR3, you just have to activate lens correction to remove distortion.
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