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Barrel Distortion


SlowSong e2
6 4.8k 29 England
9 Nov 2012 10:23AM
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).

img-1114-resized.jpg



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.

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mikehit e2
5 7.1k 11 United Kingdom
9 Nov 2012 10:51AM
Yes, all compacts are like this at the wider end. With a focal length of 6mm, think about what happens with a fish-eye lens on 35mm.
Carabosse e2
11 39.7k 269 England
9 Nov 2012 10:56AM
I'm pleased to say my Panasonic TA2 (cost 70) exhibits no barrel, or pincushion, distortion through its 4.1mm lens.

pic-of-pic.jpg

SlowSong e2
6 4.8k 29 England
9 Nov 2012 11:00AM
I would've thought at F8 it would be OK. That's as wide as the G11 and S100 go. Perhaps I should stand further away and zoom in, but then the shutter speed will be slower. Could up the ISO but the noise'd start creeping in. I guess those are the compromises with compacts.
mikehit e2
5 7.1k 11 United Kingdom
9 Nov 2012 11:07AM

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.
Carabosse e2
11 39.7k 269 England
9 Nov 2012 11:15AM
No idea Mike. The device is about as basic as you can get - I would not have thought it has any on-board processing. The sensor is indeed small: 1/4".

The pic was taken at f2.8.
cameracat 11 8.6k 61 Norfolk Island
9 Nov 2012 11:24AM
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.....Grin

That's my best guess as I'm not familiar with the little Canon jobs....Wink
JJGEE 9 6.4k 18 England
9 Nov 2012 11:44AM

Quote:Perhaps I should stand further away and zoom in, but then the shutter speed will be slower.

Why would the shutter speed be slower just because you stood further away and zoomed in ?
Sooty_1 4 1.3k 203 United Kingdom
9 Nov 2012 12:15PM
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
6 4.8k 29 England
9 Nov 2012 12:21PM
Raw through E11. I understand all the above points but I was just surprised the barelling was so noticeable. I'll try some alternatives just to see what the optimum focal length/aperture settings are some time.

You've got the S100 haven't you CB? How do you find it?
Cheers Smile
SlowSong e2
6 4.8k 29 England
9 Nov 2012 12:36PM
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

img-0828-resized.jpg

Carabosse e2
11 39.7k 269 England
9 Nov 2012 8:12PM

Quote:You've got the S100 haven't you CB? How do you find it?


Sorry not to have replied before - it's been one of those days! Grin

Pic below taken with the S100. Uncropped, aperture f2.2, RAW. Widest end of the zoom - 5.2mm (FF=24mm). There is a touch of barrel distortion, but nothing I would worry about particularly. As you would say, very easily corrected.

I think it is one of those things which comes from a compromise lens: (FF=) 24-120mm on the Canon S100. The lens on my Panny TA2 is a " prime", i.e. fixed focal length 4.1mm (FF=39mm).

pic-s100.jpg

SlowSong e2
6 4.8k 29 England
9 Nov 2012 10:09PM
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. Smile
x
strawman 11 22.0k 16 United Kingdom
9 Nov 2012 11:16PM
On my S95 jpeg images are corrected for barrel distortion but not RAW images. But if you use DPP it has the ability to correct the distortion for you on RAW images also.
SlowSong e2
6 4.8k 29 England
10 Nov 2012 8:56AM
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.

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