lens correction for Elph 300 and other Canon wide angle lenses - RAW Shooting and Processing - CHDK Forum
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lens correction for Elph 300 and other Canon wide angle lenses

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Offline hiker_jon

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lens correction for Elph 300 and other Canon wide angle lenses
« on: 05 / February / 2012, 14:53:29 »
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Hi,
The Elph 300 has an unusually wide angle fast lens for such a tiny camera.  Canon does some fancy distortion correction on the raw data before producing the jpeg.  If I save the raw data and develop it there is huge distortion compared with the in-camera jpeg.  Does anyone know of software that can correct for this distortion?
I imagine that this trick (using a distorted lens with correction done in software) will be more and more popular with camera manufacturers.   I am attaching an example.  One image is the in-camera jpeg the other was developed from a raw dng that I saved and developed using ufraw on my pc.

Edit:  I downloaded a newer version of ufraw and see that it does have a distortion correction, but the Elph 300 is not on its list of cameras and I don't know how to use this feature anyway.  Can anyone help with how to use a distortion correction and how to determine the parameters of the correction?
Jon
« Last Edit: 05 / February / 2012, 15:07:36 by hiker_jon »
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Offline SkyWalker9

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Re: lens correction for Elph 300 and other Canon wide angle lenses
« Reply #1 on: 05 / February / 2012, 22:04:37 »
Quote
The Elph 300 has an unusually wide angle fast lens for such a tiny camera...If I save the raw data and develop it there is huge distortion compared with the in-camera jpeg.  Does anyone know of software that can correct for this distortion?
Wide-angle lenses commonly cause the barrel distortion you are experiencing and panorama photo stitching is another area where alignment/distorion issues are common. Both can be easily corrected in post-processing. Although applications such as Lightroom can correct the distortion, "The GIMP" (or GNU Image Manipulation Program www.gimp.org) is a free, open-source image editing application that is able to correct this distortion. Here an example of how to correct the distortion using GIMP:
http://graphicssoft.about.com/od/gimp/ss/perspective.htm

Hope this helps!
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Offline hiker_jon

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Re: lens correction for Elph 300 and other Canon wide angle lenses
« Reply #2 on: 05 / February / 2012, 22:16:41 »
This is not just the usual wide angle distortion, it is much more severe.   I suspect that a special correction is needed, but I'll give the Gimp a try.
Edit: I looked at the Gimp.  It can't correct for this distortion.

Quote from: SkyWalker9 on 05 / February / 2012, 22:04:37
Quote
The Elph 300 has an unusually wide angle fast lens for such a tiny camera...If I save the raw data and develop it there is huge distortion compared with the in-camera jpeg.  Does anyone know of software that can correct for this distortion?
Wide-angle lenses commonly cause the barrel distortion you are experiencing and panorama photo stitching is another area where alignment/distorion issues are common. Both can be easily corrected in post-processing. Although applications such as Lightroom can correct the distortion, "The GIMP" (or GNU Image Manipulation Program www.gimp.org) is a free, open-source image editing application that is able to correct this distortion. Here an example of how to correct the distortion using GIMP:
http://graphicssoft.about.com/od/gimp/ss/perspective.htm

Hope this helps!

« Last Edit: 05 / February / 2012, 22:24:08 by hiker_jon »
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Offline fe50

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Re: lens correction for Elph 300 and other Canon wide angle lenses
« Reply #3 on: 06 / February / 2012, 01:18:44 »
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Offline Pauls9

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Re: lens correction for Elph 300 and other Canon wide angle lenses
« Reply #4 on: 06 / February / 2012, 04:45:46 »
The Adobe lens profile creator could be of use in conjunction with UFraw or other programs.

http://labs.adobe.com/technologies/lensprofile_creator/
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Offline hiker_jon

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Re: lens correction for Elph 300 and other Canon wide angle lenses
« Reply #5 on: 06 / February / 2012, 12:34:44 »
Rawtherapee worked pretty well.  (Although I must say the user interface is non-intuitive to say the least!) I only applied it to one image.  Don't know if each shot will require a special setting or not.

Jon


Quote from: fe50 on 06 / February / 2012, 01:18:44
* http://www.rawtherapee.com/
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Offline bhoyt

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Re: lens correction for Elph 300 and other Canon wide angle lenses
« Reply #6 on: 15 / March / 2012, 18:28:19 »
How did you convert from the CRW RAW file to DNG? I have CHDK installed on my ELPH 300 but can find anything to view or convert the CRW RAW file.
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Offline waterwingz

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Re: lens correction for Elph 300 and other Canon wide angle lenses
« Reply #7 on: 15 / March / 2012, 18:38:31 »
Quote from: bhoyt on 15 / March / 2012, 18:28:19
How did you convert from the CRW RAW file to DNG? I have CHDK installed on my ELPH 300 but can find anything to view or convert the CRW RAW file.
The easiest way is to save them as DNG in the camera in the first place.  Otherwise, you could try this : http://chdk.wikia.com/wiki/DNG4PS-2
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