Barrel Distortion

SlowSong (e2 Member)

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9 Nov 2012 - 10:23 AM

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I gave the Canon G11 another run out yesterday but was amazed when downloading the pics just how much barrel distortion there is on it. I've never noticed before and it was only the straight lines which gave the game away. I know it can be easily recitified in PS but I was just surprised. Are all compacts like this?
Example image below. Details - F8, ISO400, 1/30th, focal length 6.10 (but I don't know what that means on a compact).



I also find that when photographing flat subjects with the S100 the image is distorted although I've made sure the subject is straight when viewing the screen. What a pain.

Carabosse (e2 Member)

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9 Nov 2012 - 10:56 AM

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I'm pleased to say my Panasonic TA2 (cost £70) exhibits no barrel, or pincushion, distortion through its 4.1mm lens.

mikehit (e2 Member)

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9 Nov 2012 - 11:07 AM

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Quote: I'm pleased to say my Panasonic TA2 (cost £70) exhibits no barrel, or pincushion, distortion through its 4.1mm lens.

Is that because the on-board processing removes it?
It may also be a function of the sensor size where the TA2 sensor is smaller (I don't know if it is?) so takes information from the middle part of the lens which has less distortion.

cameracat (e2 Member)

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9 Nov 2012 - 11:24 AM

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What software are you running the images through Chris....?

I ask because, If Canon have on-board correction in the G11, It may only be read and corrected in Canons own software, ie: DPP.

Another question...Are you shooting RAW or straight jpegs....?

Last, The G11 may have some form of on-board that needs setting up in the menus.....

That's my best guess as I'm not familiar with the little Canon jobs....

Sooty_1 (Critique Team)

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9 Nov 2012 - 12:15 PM

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Maybe because the effective aperture gets smaller as the focal length gets longer. But this should be minimal at the slightly longer length needed (probably less than a stop). The distortion is usually worse at the extremes of the zoom range, and at edges of the frame, so just compose a bit looser and crop slightly in PS. And/or use a more middling focal length.

Nick

SlowSong (e2 Member)

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9 Nov 2012 - 12:36 PM

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Here's one I took with the S100. Same thing as on the G11. I admit I might have stood slightly wonky, but the distortion is very evident. I did use the widest aperture, I admit. I always leave space around images anyway in case cropping/straightening is needed - luckily. I was always taught to do this although it's against all my natural instincts.
1/8th, F4.5, ISO400, 6.10

SlowSong (e2 Member)

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9 Nov 2012 - 10:09 PM

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Ah yes, the same effect. Well, I won't worry about it, but it's something to look out for. Thanks for the comparison CB.
x

SlowSong (e2 Member)

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10 Nov 2012 - 8:56 AM

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Hi Strawman. Sorry but I don't quite understand. Both my jpgs and RAWs have the same distortion. I can't see how one can be different to the other.
So are you saying that you can set something in-camera to correct the distortion? I'm amazed if you can as surely if you can correct in-camera it should be correct at the outset.

I'm a bit loathe to use DPP seeing as I've paid for ACR, but it is easy to correct in PS anyway. That isn't my query really.